diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs index 7ee881b0639da..eaef4c7b54a62 100644 --- a/compiler/rustc_index/src/lib.rs +++ b/compiler/rustc_index/src/lib.rs @@ -1,5 +1,4 @@ #![feature(allow_internal_unstable)] -#![feature(bool_to_option)] #![feature(const_fn)] #![feature(const_panic)] #![feature(extend_one)] diff --git a/compiler/rustc_metadata/src/lib.rs b/compiler/rustc_metadata/src/lib.rs index 77766be7397c7..2560cfa74624a 100644 --- a/compiler/rustc_metadata/src/lib.rs +++ b/compiler/rustc_metadata/src/lib.rs @@ -1,5 +1,4 @@ #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")] -#![feature(bool_to_option)] #![feature(core_intrinsics)] #![feature(crate_visibility_modifier)] #![feature(drain_filter)] diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs index f125a12147af5..8a6b0230023ff 100644 --- a/compiler/rustc_parse/src/lib.rs +++ b/compiler/rustc_parse/src/lib.rs @@ -1,6 +1,5 @@ //! The main parser interface. -#![feature(bool_to_option)] #![feature(crate_visibility_modifier)] #![feature(bindings_after_at)] #![feature(iter_order_by)] diff --git a/library/alloc/src/collections/btree/append.rs b/library/alloc/src/collections/btree/append.rs index d3edcd0b87e0f..bd99c4ed2f14e 100644 --- a/library/alloc/src/collections/btree/append.rs +++ b/library/alloc/src/collections/btree/append.rs @@ -67,7 +67,7 @@ impl Root { // Push key-value pair and new right subtree. let tree_height = open_node.height() - 1; - let mut right_tree = Root::new_leaf(); + let mut right_tree = Root::new(); for _ in 0..tree_height { right_tree.push_internal_level(); } diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs index a9e416875905c..383f4487aff3d 100644 --- a/library/alloc/src/collections/btree/map.rs +++ b/library/alloc/src/collections/btree/map.rs @@ -9,7 +9,7 @@ use core::ops::{Index, RangeBounds}; use core::ptr; use super::borrow::DormantMutRef; -use super::node::{self, marker, ForceResult::*, Handle, NodeRef}; +use super::node::{self, marker, ForceResult::*, Handle, NodeRef, Root}; use super::search::{self, SearchResult::*}; use super::unwrap_unchecked; @@ -128,7 +128,7 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT; /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub struct BTreeMap { - root: Option>, + root: Option>, length: usize, } @@ -145,7 +145,7 @@ unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap { impl Clone for BTreeMap { fn clone(&self) -> BTreeMap { fn clone_subtree<'a, K: Clone, V: Clone>( - node: node::NodeRef, K, V, marker::LeafOrInternal>, + node: NodeRef, K, V, marker::LeafOrInternal>, ) -> BTreeMap where K: 'a, @@ -153,7 +153,7 @@ impl Clone for BTreeMap { { match node.force() { Leaf(leaf) => { - let mut out_tree = BTreeMap { root: Some(node::Root::new_leaf()), length: 0 }; + let mut out_tree = BTreeMap { root: Some(Root::new()), length: 0 }; { let root = out_tree.root.as_mut().unwrap(); // unwrap succeeds because we just wrapped @@ -198,7 +198,7 @@ impl Clone for BTreeMap { (root, length) }; - out_node.push(k, v, subroot.unwrap_or_else(node::Root::new_leaf)); + out_node.push(k, v, subroot.unwrap_or_else(Root::new)); out_tree.length += 1 + sublength; } } @@ -1558,7 +1558,7 @@ pub(super) struct DrainFilterInner<'a, K: 'a, V: 'a> { length: &'a mut usize, /// Burried reference to the root field in the borrowed map. /// Wrapped in `Option` to allow drop handler to `take` it. - dormant_root: Option>>, + dormant_root: Option>>, /// Contains a leaf edge preceding the next element to be returned, or the last leaf edge. /// Empty if the map has no root, if iteration went beyond the last leaf edge, /// or if a panic occurred in the predicate. @@ -2160,8 +2160,8 @@ impl BTreeMap { /// If the root node is the empty (non-allocated) root node, allocate our /// own node. Is an associated function to avoid borrowing the entire BTreeMap. - fn ensure_is_owned(root: &mut Option>) -> &mut node::Root { - root.get_or_insert_with(node::Root::new_leaf) + fn ensure_is_owned(root: &mut Option>) -> &mut Root { + root.get_or_insert_with(Root::new) } } diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs index f15959a1665dd..23cd4f3d83d62 100644 --- a/library/alloc/src/collections/btree/map/tests.rs +++ b/library/alloc/src/collections/btree/map/tests.rs @@ -6,13 +6,14 @@ use crate::fmt::Debug; use crate::rc::Rc; use crate::string::{String, ToString}; use crate::vec::Vec; +use std::cmp::Ordering; use std::convert::TryFrom; use std::iter::{self, FromIterator}; use std::mem; use std::ops::Bound::{self, Excluded, Included, Unbounded}; use std::ops::RangeBounds; use std::panic::{catch_unwind, AssertUnwindSafe}; -use std::sync::atomic::{AtomicUsize, Ordering}; +use std::sync::atomic::{AtomicUsize, Ordering::SeqCst}; mod ord_chaos; use ord_chaos::{Cyclic3, Governed, Governor}; @@ -56,24 +57,23 @@ impl BTreeMap { assert!(root_node.ascend().is_err()); root_node.assert_back_pointers(); - // Check consistenty of `length` and some of the navigation. + // Check consistency of `length` with what navigation code encounters. assert_eq!(self.length, root_node.calc_length()); - assert_eq!(self.length, self.keys().count()); // Lastly, check the invariant causing the least harm. root_node.assert_min_len(if root_node.height() > 0 { 1 } else { 0 }); } else { - // Check consistenty of `length` and some of the navigation. assert_eq!(self.length, 0); - assert_eq!(self.length, self.keys().count()); } + + // Check that `assert_strictly_ascending` will encounter all keys. + assert_eq!(self.length, self.keys().count()); } // Panics if the map is corrupted or if the keys are not in strictly // ascending order, in the current opinion of the `Ord` implementation. - // If the `Ord` implementation does not honor transitivity, this method - // does not guarantee that all the keys are unique, just that adjacent - // keys are unique. + // If the `Ord` implementation violates transitivity, this method does not + // guarantee that all keys are unique, just that adjacent keys are unique. fn check(&self) where K: Debug + Ord, @@ -879,6 +879,7 @@ mod test_drain_filter { map.check(); } + // Explicitly consumes the iterator, where most test cases drop it instantly. #[test] fn consumed_keeping_all() { let pairs = (0..3).map(|i| (i, i)); @@ -887,6 +888,7 @@ mod test_drain_filter { map.check(); } + // Explicitly consumes the iterator, where most test cases drop it instantly. #[test] fn consumed_removing_all() { let pairs = (0..3).map(|i| (i, i)); @@ -896,15 +898,7 @@ mod test_drain_filter { map.check(); } - #[test] - fn dropped_removing_all() { - let pairs = (0..3).map(|i| (i, i)); - let mut map: BTreeMap<_, _> = pairs.collect(); - map.drain_filter(|_, _| true); - assert!(map.is_empty()); - map.check(); - } - + // Explicitly consumes the iterator and modifies values through it. #[test] fn mutating_and_keeping() { let pairs = (0..3).map(|i| (i, i)); @@ -921,6 +915,7 @@ mod test_drain_filter { map.check(); } + // Explicitly consumes the iterator and modifies values through it. #[test] fn mutating_and_removing() { let pairs = (0..3).map(|i| (i, i)); @@ -1094,7 +1089,7 @@ mod test_drain_filter { struct D; impl Drop for D { fn drop(&mut self) { - if DROPS.fetch_add(1, Ordering::SeqCst) == 1 { + if DROPS.fetch_add(1, SeqCst) == 1 { panic!("panic in `drop`"); } } @@ -1105,14 +1100,14 @@ mod test_drain_filter { catch_unwind(move || { drop(map.drain_filter(|i, _| { - PREDS.fetch_add(1usize << i, Ordering::SeqCst); + PREDS.fetch_add(1usize << i, SeqCst); true })) }) .unwrap_err(); - assert_eq!(PREDS.load(Ordering::SeqCst), 0x011); - assert_eq!(DROPS.load(Ordering::SeqCst), 3); + assert_eq!(PREDS.load(SeqCst), 0x011); + assert_eq!(DROPS.load(SeqCst), 3); } #[test] @@ -1123,7 +1118,7 @@ mod test_drain_filter { struct D; impl Drop for D { fn drop(&mut self) { - DROPS.fetch_add(1, Ordering::SeqCst); + DROPS.fetch_add(1, SeqCst); } } @@ -1132,7 +1127,7 @@ mod test_drain_filter { catch_unwind(AssertUnwindSafe(|| { drop(map.drain_filter(|i, _| { - PREDS.fetch_add(1usize << i, Ordering::SeqCst); + PREDS.fetch_add(1usize << i, SeqCst); match i { 0 => true, _ => panic!(), @@ -1141,8 +1136,8 @@ mod test_drain_filter { })) .unwrap_err(); - assert_eq!(PREDS.load(Ordering::SeqCst), 0x011); - assert_eq!(DROPS.load(Ordering::SeqCst), 1); + assert_eq!(PREDS.load(SeqCst), 0x011); + assert_eq!(DROPS.load(SeqCst), 1); assert_eq!(map.len(), 2); assert_eq!(map.first_entry().unwrap().key(), &4); assert_eq!(map.last_entry().unwrap().key(), &8); @@ -1158,7 +1153,7 @@ mod test_drain_filter { struct D; impl Drop for D { fn drop(&mut self) { - DROPS.fetch_add(1, Ordering::SeqCst); + DROPS.fetch_add(1, SeqCst); } } @@ -1167,7 +1162,7 @@ mod test_drain_filter { { let mut it = map.drain_filter(|i, _| { - PREDS.fetch_add(1usize << i, Ordering::SeqCst); + PREDS.fetch_add(1usize << i, SeqCst); match i { 0 => true, _ => panic!(), @@ -1180,8 +1175,8 @@ mod test_drain_filter { assert!(matches!(result, Ok(None))); } - assert_eq!(PREDS.load(Ordering::SeqCst), 0x011); - assert_eq!(DROPS.load(Ordering::SeqCst), 1); + assert_eq!(PREDS.load(SeqCst), 0x011); + assert_eq!(DROPS.load(SeqCst), 1); assert_eq!(map.len(), 2); assert_eq!(map.first_entry().unwrap().key(), &4); assert_eq!(map.last_entry().unwrap().key(), &8); @@ -1315,8 +1310,6 @@ fn test_zst() { // undefined. #[test] fn test_bad_zst() { - use std::cmp::Ordering; - #[derive(Clone, Copy, Debug)] struct Bad; @@ -1763,7 +1756,7 @@ fn test_append_drop_leak() { impl Drop for D { fn drop(&mut self) { - if DROPS.fetch_add(1, Ordering::SeqCst) == 0 { + if DROPS.fetch_add(1, SeqCst) == 0 { panic!("panic in `drop`"); } } @@ -1779,7 +1772,7 @@ fn test_append_drop_leak() { catch_unwind(move || left.append(&mut right)).unwrap_err(); - assert_eq!(DROPS.load(Ordering::SeqCst), 4); // Rust issue #47949 ate one little piggy + assert_eq!(DROPS.load(SeqCst), 4); // Rust issue #47949 ate one little piggy } #[test] @@ -1894,7 +1887,7 @@ fn test_into_iter_drop_leak_height_0() { impl Drop for D { fn drop(&mut self) { - if DROPS.fetch_add(1, Ordering::SeqCst) == 3 { + if DROPS.fetch_add(1, SeqCst) == 3 { panic!("panic in `drop`"); } } @@ -1909,7 +1902,7 @@ fn test_into_iter_drop_leak_height_0() { catch_unwind(move || drop(map.into_iter())).unwrap_err(); - assert_eq!(DROPS.load(Ordering::SeqCst), 5); + assert_eq!(DROPS.load(SeqCst), 5); } #[test] @@ -1921,18 +1914,18 @@ fn test_into_iter_drop_leak_height_1() { struct D; impl Drop for D { fn drop(&mut self) { - if DROPS.fetch_add(1, Ordering::SeqCst) == PANIC_POINT.load(Ordering::SeqCst) { + if DROPS.fetch_add(1, SeqCst) == PANIC_POINT.load(SeqCst) { panic!("panic in `drop`"); } } } for panic_point in vec![0, 1, size - 2, size - 1] { - DROPS.store(0, Ordering::SeqCst); - PANIC_POINT.store(panic_point, Ordering::SeqCst); + DROPS.store(0, SeqCst); + PANIC_POINT.store(panic_point, SeqCst); let map: BTreeMap<_, _> = (0..size).map(|i| (i, D)).collect(); catch_unwind(move || drop(map.into_iter())).unwrap_err(); - assert_eq!(DROPS.load(Ordering::SeqCst), size); + assert_eq!(DROPS.load(SeqCst), size); } } diff --git a/library/alloc/src/collections/btree/map/tests/ord_chaos.rs b/library/alloc/src/collections/btree/map/tests/ord_chaos.rs index 91d1d6ea9ef38..96ce7c1579046 100644 --- a/library/alloc/src/collections/btree/map/tests/ord_chaos.rs +++ b/library/alloc/src/collections/btree/map/tests/ord_chaos.rs @@ -2,6 +2,7 @@ use std::cell::Cell; use std::cmp::Ordering::{self, *}; use std::ptr; +// Minimal type with an `Ord` implementation violating transitivity. #[derive(Debug)] pub enum Cyclic3 { A, @@ -34,6 +35,7 @@ impl PartialEq for Cyclic3 { impl Eq for Cyclic3 {} +// Controls the ordering of values wrapped by `Governed`. #[derive(Debug)] pub struct Governor { flipped: Cell, @@ -49,6 +51,9 @@ impl Governor { } } +// Type with an `Ord` implementation that forms a total order at any moment +// (assuming that `T` respects total order), but can suddenly be made to invert +// that total order. #[derive(Debug)] pub struct Governed<'a, T>(pub T, pub &'a Governor); diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs index 4658629753da2..e3e555a72de02 100644 --- a/library/alloc/src/collections/btree/node.rs +++ b/library/alloc/src/collections/btree/node.rs @@ -134,13 +134,13 @@ pub type Root = NodeRef; impl Root { /// Returns a new owned tree, with its own root node that is initially empty. - pub fn new_leaf() -> Self { - NodeRef::new().forget_type() + pub fn new() -> Self { + NodeRef::new_leaf().forget_type() } } impl NodeRef { - fn new() -> Self { + fn new_leaf() -> Self { Self::from_new_leaf(Box::new(unsafe { LeafNode::new() })) } diff --git a/library/alloc/src/collections/btree/node/tests.rs b/library/alloc/src/collections/btree/node/tests.rs index bbf35891b568f..6886962106b02 100644 --- a/library/alloc/src/collections/btree/node/tests.rs +++ b/library/alloc/src/collections/btree/node/tests.rs @@ -74,12 +74,12 @@ fn test_splitpoint() { #[test] fn test_partial_cmp_eq() { - let mut root1 = NodeRef::new(); + let mut root1 = NodeRef::new_leaf(); let mut leaf1 = root1.borrow_mut(); leaf1.push(1, ()); let mut root1 = root1.forget_type(); root1.push_internal_level(); - let root2 = Root::new_leaf(); + let root2 = Root::new(); root1.reborrow().assert_back_pointers(); root2.reborrow().assert_back_pointers(); diff --git a/library/alloc/src/collections/btree/search.rs b/library/alloc/src/collections/btree/search.rs index 701d5ec73e218..93de2d829ac8d 100644 --- a/library/alloc/src/collections/btree/search.rs +++ b/library/alloc/src/collections/btree/search.rs @@ -50,7 +50,7 @@ where { match search_linear(&node, key) { (idx, true) => Found(unsafe { Handle::new_kv(node, idx) }), - (idx, false) => SearchResult::GoDown(unsafe { Handle::new_edge(node, idx) }), + (idx, false) => GoDown(unsafe { Handle::new_edge(node, idx) }), } } diff --git a/library/alloc/src/collections/btree/set/tests.rs b/library/alloc/src/collections/btree/set/tests.rs index ef40a048a382e..4d05bc4ebfa1e 100644 --- a/library/alloc/src/collections/btree/set/tests.rs +++ b/library/alloc/src/collections/btree/set/tests.rs @@ -1,9 +1,10 @@ use super::super::DeterministicRng; use super::*; use crate::vec::Vec; +use std::cmp::Ordering; use std::iter::FromIterator; use std::panic::{catch_unwind, AssertUnwindSafe}; -use std::sync::atomic::{AtomicU32, Ordering}; +use std::sync::atomic::{AtomicU32, Ordering::SeqCst}; #[test] fn test_clone_eq() { @@ -355,7 +356,7 @@ fn test_drain_filter_drop_panic_leak() { struct D(i32); impl Drop for D { fn drop(&mut self) { - if DROPS.fetch_add(1, Ordering::SeqCst) == 1 { + if DROPS.fetch_add(1, SeqCst) == 1 { panic!("panic in `drop`"); } } @@ -368,14 +369,14 @@ fn test_drain_filter_drop_panic_leak() { catch_unwind(move || { drop(set.drain_filter(|d| { - PREDS.fetch_add(1u32 << d.0, Ordering::SeqCst); + PREDS.fetch_add(1u32 << d.0, SeqCst); true })) }) .ok(); - assert_eq!(PREDS.load(Ordering::SeqCst), 0x011); - assert_eq!(DROPS.load(Ordering::SeqCst), 3); + assert_eq!(PREDS.load(SeqCst), 0x011); + assert_eq!(DROPS.load(SeqCst), 3); } #[test] @@ -387,7 +388,7 @@ fn test_drain_filter_pred_panic_leak() { struct D(i32); impl Drop for D { fn drop(&mut self) { - DROPS.fetch_add(1, Ordering::SeqCst); + DROPS.fetch_add(1, SeqCst); } } @@ -398,7 +399,7 @@ fn test_drain_filter_pred_panic_leak() { catch_unwind(AssertUnwindSafe(|| { drop(set.drain_filter(|d| { - PREDS.fetch_add(1u32 << d.0, Ordering::SeqCst); + PREDS.fetch_add(1u32 << d.0, SeqCst); match d.0 { 0 => true, _ => panic!(), @@ -407,8 +408,8 @@ fn test_drain_filter_pred_panic_leak() { })) .ok(); - assert_eq!(PREDS.load(Ordering::SeqCst), 0x011); - assert_eq!(DROPS.load(Ordering::SeqCst), 1); + assert_eq!(PREDS.load(SeqCst), 0x011); + assert_eq!(DROPS.load(SeqCst), 1); assert_eq!(set.len(), 2); assert_eq!(set.first().unwrap().0, 4); assert_eq!(set.last().unwrap().0, 8); @@ -498,8 +499,6 @@ fn test_extend_ref() { #[test] fn test_recovery() { - use std::cmp::Ordering; - #[derive(Debug)] struct Foo(&'static str, i32); diff --git a/library/core/src/alloc/layout.rs b/library/core/src/alloc/layout.rs index 2258d9614d53b..339d85902b83f 100644 --- a/library/core/src/alloc/layout.rs +++ b/library/core/src/alloc/layout.rs @@ -50,7 +50,7 @@ impl Layout { /// must not overflow (i.e., the rounded value must be less than /// or equal to `usize::MAX`). #[stable(feature = "alloc_layout", since = "1.28.0")] - #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")] + #[rustc_const_stable(feature = "const_alloc_layout", since = "1.50.0")] #[inline] pub const fn from_size_align(size: usize, align: usize) -> Result { if !align.is_power_of_two() { @@ -96,7 +96,7 @@ impl Layout { /// The minimum size in bytes for a memory block of this layout. #[stable(feature = "alloc_layout", since = "1.28.0")] - #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")] + #[rustc_const_stable(feature = "const_alloc_layout", since = "1.50.0")] #[inline] pub const fn size(&self) -> usize { self.size_ @@ -104,7 +104,7 @@ impl Layout { /// The minimum byte alignment for a memory block of this layout. #[stable(feature = "alloc_layout", since = "1.28.0")] - #[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")] + #[rustc_const_stable(feature = "const_alloc_layout", since = "1.50.0")] #[inline] pub const fn align(&self) -> usize { self.align_.get() diff --git a/library/core/src/bool.rs b/library/core/src/bool.rs index 6e0865e8653b7..00164c631b305 100644 --- a/library/core/src/bool.rs +++ b/library/core/src/bool.rs @@ -23,12 +23,10 @@ impl bool { /// # Examples /// /// ``` - /// #![feature(bool_to_option)] - /// /// assert_eq!(false.then(|| 0), None); /// assert_eq!(true.then(|| 0), Some(0)); /// ``` - #[unstable(feature = "bool_to_option", issue = "64260")] + #[stable(feature = "lazy_bool_to_option", since = "1.50.0")] #[inline] pub fn then T>(self, f: F) -> Option { if self { Some(f()) } else { None } diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs index b2afb702eeb86..e1b6307613b73 100644 --- a/library/core/src/cell.rs +++ b/library/core/src/cell.rs @@ -1027,7 +1027,6 @@ impl RefCell { /// # Examples /// /// ``` - /// #![feature(refcell_take)] /// use std::cell::RefCell; /// /// let c = RefCell::new(5); @@ -1036,7 +1035,7 @@ impl RefCell { /// assert_eq!(five, 5); /// assert_eq!(c.into_inner(), 0); /// ``` - #[unstable(feature = "refcell_take", issue = "71395")] + #[stable(feature = "refcell_take", since = "1.50.0")] pub fn take(&self) -> T { self.replace(Default::default()) } diff --git a/library/core/src/iter/adapters/chain.rs b/library/core/src/iter/adapters/chain.rs index 2e070d7122442..9753e1b43ba95 100644 --- a/library/core/src/iter/adapters/chain.rs +++ b/library/core/src/iter/adapters/chain.rs @@ -1,6 +1,5 @@ use crate::iter::{DoubleEndedIterator, FusedIterator, Iterator, TrustedLen}; -use crate::ops::Try; -use crate::usize; +use crate::{ops::Try, usize}; /// An iterator that links two iterators together, in a chain. /// diff --git a/library/core/src/iter/adapters/cloned.rs b/library/core/src/iter/adapters/cloned.rs new file mode 100644 index 0000000000000..7da47dcd2d147 --- /dev/null +++ b/library/core/src/iter/adapters/cloned.rs @@ -0,0 +1,139 @@ +use crate::iter::adapters::{zip::try_get_unchecked, TrustedRandomAccess}; +use crate::iter::{FusedIterator, TrustedLen}; +use crate::ops::Try; + +/// An iterator that clones the elements of an underlying iterator. +/// +/// This `struct` is created by the [`cloned`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`cloned`]: Iterator::cloned +/// [`Iterator`]: trait.Iterator.html +#[stable(feature = "iter_cloned", since = "1.1.0")] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[derive(Clone, Debug)] +pub struct Cloned { + it: I, +} + +impl Cloned { + pub(in crate::iter) fn new(it: I) -> Cloned { + Cloned { it } + } +} + +fn clone_try_fold(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R { + move |acc, elt| f(acc, elt.clone()) +} + +#[stable(feature = "iter_cloned", since = "1.1.0")] +impl<'a, I, T: 'a> Iterator for Cloned +where + I: Iterator, + T: Clone, +{ + type Item = T; + + fn next(&mut self) -> Option { + self.it.next().cloned() + } + + fn size_hint(&self) -> (usize, Option) { + self.it.size_hint() + } + + fn try_fold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.it.try_fold(init, clone_try_fold(f)) + } + + fn fold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.it.map(T::clone).fold(init, f) + } + + unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T + where + Self: TrustedRandomAccess, + { + // SAFETY: the caller must uphold the contract for + // `Iterator::__iterator_get_unchecked`. + unsafe { try_get_unchecked(&mut self.it, idx).clone() } + } +} + +#[stable(feature = "iter_cloned", since = "1.1.0")] +impl<'a, I, T: 'a> DoubleEndedIterator for Cloned +where + I: DoubleEndedIterator, + T: Clone, +{ + fn next_back(&mut self) -> Option { + self.it.next_back().cloned() + } + + fn try_rfold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.it.try_rfold(init, clone_try_fold(f)) + } + + fn rfold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.it.map(T::clone).rfold(init, f) + } +} + +#[stable(feature = "iter_cloned", since = "1.1.0")] +impl<'a, I, T: 'a> ExactSizeIterator for Cloned +where + I: ExactSizeIterator, + T: Clone, +{ + fn len(&self) -> usize { + self.it.len() + } + + fn is_empty(&self) -> bool { + self.it.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl<'a, I, T: 'a> FusedIterator for Cloned +where + I: FusedIterator, + T: Clone, +{ +} + +#[doc(hidden)] +#[unstable(feature = "trusted_random_access", issue = "none")] +unsafe impl TrustedRandomAccess for Cloned +where + I: TrustedRandomAccess, +{ + #[inline] + fn may_have_side_effect() -> bool { + true + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<'a, I, T: 'a> TrustedLen for Cloned +where + I: TrustedLen, + T: Clone, +{ +} diff --git a/library/core/src/iter/adapters/copied.rs b/library/core/src/iter/adapters/copied.rs new file mode 100644 index 0000000000000..46f22354111a6 --- /dev/null +++ b/library/core/src/iter/adapters/copied.rs @@ -0,0 +1,155 @@ +use crate::iter::adapters::{zip::try_get_unchecked, TrustedRandomAccess}; +use crate::iter::{FusedIterator, TrustedLen}; +use crate::ops::Try; + +/// An iterator that copies the elements of an underlying iterator. +/// +/// This `struct` is created by the [`copied`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`copied`]: Iterator::copied +/// [`Iterator`]: trait.Iterator.html +#[stable(feature = "iter_copied", since = "1.36.0")] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[derive(Clone, Debug)] +pub struct Copied { + it: I, +} + +impl Copied { + pub(in crate::iter) fn new(it: I) -> Copied { + Copied { it } + } +} + +fn copy_fold(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, &T) -> Acc { + move |acc, &elt| f(acc, elt) +} + +fn copy_try_fold(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R { + move |acc, &elt| f(acc, elt) +} + +#[stable(feature = "iter_copied", since = "1.36.0")] +impl<'a, I, T: 'a> Iterator for Copied +where + I: Iterator, + T: Copy, +{ + type Item = T; + + fn next(&mut self) -> Option { + self.it.next().copied() + } + + fn size_hint(&self) -> (usize, Option) { + self.it.size_hint() + } + + fn try_fold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.it.try_fold(init, copy_try_fold(f)) + } + + fn fold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.it.fold(init, copy_fold(f)) + } + + fn nth(&mut self, n: usize) -> Option { + self.it.nth(n).copied() + } + + fn last(self) -> Option { + self.it.last().copied() + } + + fn count(self) -> usize { + self.it.count() + } + + unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T + where + Self: TrustedRandomAccess, + { + // SAFETY: the caller must uphold the contract for + // `Iterator::__iterator_get_unchecked`. + *unsafe { try_get_unchecked(&mut self.it, idx) } + } +} + +#[stable(feature = "iter_copied", since = "1.36.0")] +impl<'a, I, T: 'a> DoubleEndedIterator for Copied +where + I: DoubleEndedIterator, + T: Copy, +{ + fn next_back(&mut self) -> Option { + self.it.next_back().copied() + } + + fn try_rfold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.it.try_rfold(init, copy_try_fold(f)) + } + + fn rfold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.it.rfold(init, copy_fold(f)) + } +} + +#[stable(feature = "iter_copied", since = "1.36.0")] +impl<'a, I, T: 'a> ExactSizeIterator for Copied +where + I: ExactSizeIterator, + T: Copy, +{ + fn len(&self) -> usize { + self.it.len() + } + + fn is_empty(&self) -> bool { + self.it.is_empty() + } +} + +#[stable(feature = "iter_copied", since = "1.36.0")] +impl<'a, I, T: 'a> FusedIterator for Copied +where + I: FusedIterator, + T: Copy, +{ +} + +#[doc(hidden)] +#[unstable(feature = "trusted_random_access", issue = "none")] +unsafe impl TrustedRandomAccess for Copied +where + I: TrustedRandomAccess, +{ + #[inline] + fn may_have_side_effect() -> bool { + I::may_have_side_effect() + } +} + +#[stable(feature = "iter_copied", since = "1.36.0")] +unsafe impl<'a, I, T: 'a> TrustedLen for Copied +where + I: TrustedLen, + T: Copy, +{ +} diff --git a/library/core/src/iter/adapters/cycle.rs b/library/core/src/iter/adapters/cycle.rs new file mode 100644 index 0000000000000..6e9a011f819af --- /dev/null +++ b/library/core/src/iter/adapters/cycle.rs @@ -0,0 +1,87 @@ +use crate::{iter::FusedIterator, ops::Try}; + +/// An iterator that repeats endlessly. +/// +/// This `struct` is created by the [`cycle`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`cycle`]: Iterator::cycle +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Cycle { + orig: I, + iter: I, +} + +impl Cycle { + pub(in crate::iter) fn new(iter: I) -> Cycle { + Cycle { orig: iter.clone(), iter } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Cycle +where + I: Clone + Iterator, +{ + type Item = ::Item; + + #[inline] + fn next(&mut self) -> Option<::Item> { + match self.iter.next() { + None => { + self.iter = self.orig.clone(); + self.iter.next() + } + y => y, + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + // the cycle iterator is either empty or infinite + match self.orig.size_hint() { + sz @ (0, Some(0)) => sz, + (0, _) => (0, None), + _ => (usize::MAX, None), + } + } + + #[inline] + fn try_fold(&mut self, mut acc: Acc, mut f: F) -> R + where + F: FnMut(Acc, Self::Item) -> R, + R: Try, + { + // fully iterate the current iterator. this is necessary because + // `self.iter` may be empty even when `self.orig` isn't + acc = self.iter.try_fold(acc, &mut f)?; + self.iter = self.orig.clone(); + + // complete a full cycle, keeping track of whether the cycled + // iterator is empty or not. we need to return early in case + // of an empty iterator to prevent an infinite loop + let mut is_empty = true; + acc = self.iter.try_fold(acc, |acc, x| { + is_empty = false; + f(acc, x) + })?; + + if is_empty { + return try { acc }; + } + + loop { + self.iter = self.orig.clone(); + acc = self.iter.try_fold(acc, &mut f)?; + } + } + + // No `fold` override, because `fold` doesn't make much sense for `Cycle`, + // and we can't do anything better than the default. +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Cycle where I: Clone + Iterator {} diff --git a/library/core/src/iter/adapters/enumerate.rs b/library/core/src/iter/adapters/enumerate.rs new file mode 100644 index 0000000000000..5978c2da98c35 --- /dev/null +++ b/library/core/src/iter/adapters/enumerate.rs @@ -0,0 +1,238 @@ +use crate::iter::adapters::{zip::try_get_unchecked, SourceIter, TrustedRandomAccess}; +use crate::iter::{FusedIterator, InPlaceIterable, TrustedLen}; +use crate::ops::{Add, AddAssign, Try}; + +/// An iterator that yields the current count and the element during iteration. +/// +/// This `struct` is created by the [`enumerate`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`enumerate`]: Iterator::enumerate +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Enumerate { + iter: I, + count: usize, +} +impl Enumerate { + pub(in crate::iter) fn new(iter: I) -> Enumerate { + Enumerate { iter, count: 0 } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Enumerate +where + I: Iterator, +{ + type Item = (usize, ::Item); + + /// # Overflow Behavior + /// + /// The method does no guarding against overflows, so enumerating more than + /// `usize::MAX` elements either produces the wrong result or panics. If + /// debug assertions are enabled, a panic is guaranteed. + /// + /// # Panics + /// + /// Might panic if the index of the element overflows a `usize`. + #[inline] + fn next(&mut self) -> Option<(usize, ::Item)> { + let a = self.iter.next()?; + let i = self.count; + // Possible undefined overflow. + AddAssign::add_assign(&mut self.count, 1); + Some((i, a)) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<(usize, I::Item)> { + let a = self.iter.nth(n)?; + // Possible undefined overflow. + let i = Add::add(self.count, n); + self.count = Add::add(i, 1); + Some((i, a)) + } + + #[inline] + fn count(self) -> usize { + self.iter.count() + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + #[inline] + fn enumerate<'a, T, Acc, R>( + count: &'a mut usize, + mut fold: impl FnMut(Acc, (usize, T)) -> R + 'a, + ) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| { + let acc = fold(acc, (*count, item)); + // Possible undefined overflow. + AddAssign::add_assign(count, 1); + acc + } + } + + self.iter.try_fold(init, enumerate(&mut self.count, fold)) + } + + #[inline] + fn fold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn enumerate( + mut count: usize, + mut fold: impl FnMut(Acc, (usize, T)) -> Acc, + ) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| { + let acc = fold(acc, (count, item)); + // Possible undefined overflow. + AddAssign::add_assign(&mut count, 1); + acc + } + } + + self.iter.fold(init, enumerate(self.count, fold)) + } + + unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> ::Item + where + Self: TrustedRandomAccess, + { + // SAFETY: the caller must uphold the contract for + // `Iterator::__iterator_get_unchecked`. + let value = unsafe { try_get_unchecked(&mut self.iter, idx) }; + (Add::add(self.count, idx), value) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Enumerate +where + I: ExactSizeIterator + DoubleEndedIterator, +{ + #[inline] + fn next_back(&mut self) -> Option<(usize, ::Item)> { + let a = self.iter.next_back()?; + let len = self.iter.len(); + // Can safely add, `ExactSizeIterator` promises that the number of + // elements fits into a `usize`. + Some((self.count + len, a)) + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<(usize, ::Item)> { + let a = self.iter.nth_back(n)?; + let len = self.iter.len(); + // Can safely add, `ExactSizeIterator` promises that the number of + // elements fits into a `usize`. + Some((self.count + len, a)) + } + + #[inline] + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + // Can safely add and subtract the count, as `ExactSizeIterator` promises + // that the number of elements fits into a `usize`. + fn enumerate( + mut count: usize, + mut fold: impl FnMut(Acc, (usize, T)) -> R, + ) -> impl FnMut(Acc, T) -> R { + move |acc, item| { + count -= 1; + fold(acc, (count, item)) + } + } + + let count = self.count + self.iter.len(); + self.iter.try_rfold(init, enumerate(count, fold)) + } + + #[inline] + fn rfold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + // Can safely add and subtract the count, as `ExactSizeIterator` promises + // that the number of elements fits into a `usize`. + fn enumerate( + mut count: usize, + mut fold: impl FnMut(Acc, (usize, T)) -> Acc, + ) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| { + count -= 1; + fold(acc, (count, item)) + } + } + + let count = self.count + self.iter.len(); + self.iter.rfold(init, enumerate(count, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Enumerate +where + I: ExactSizeIterator, +{ + fn len(&self) -> usize { + self.iter.len() + } + + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[doc(hidden)] +#[unstable(feature = "trusted_random_access", issue = "none")] +unsafe impl TrustedRandomAccess for Enumerate +where + I: TrustedRandomAccess, +{ + fn may_have_side_effect() -> bool { + I::may_have_side_effect() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Enumerate where I: FusedIterator {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Enumerate where I: TrustedLen {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Enumerate +where + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Enumerate {} diff --git a/library/core/src/iter/adapters/filter.rs b/library/core/src/iter/adapters/filter.rs new file mode 100644 index 0000000000000..f8d684fcdda46 --- /dev/null +++ b/library/core/src/iter/adapters/filter.rs @@ -0,0 +1,152 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::Try; + +/// An iterator that filters the elements of `iter` with `predicate`. +/// +/// This `struct` is created by the [`filter`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`filter`]: Iterator::filter +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct Filter { + iter: I, + predicate: P, +} +impl Filter { + pub(in crate::iter) fn new(iter: I, predicate: P) -> Filter { + Filter { iter, predicate } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for Filter { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Filter").field("iter", &self.iter).finish() + } +} + +fn filter_fold( + mut predicate: impl FnMut(&T) -> bool, + mut fold: impl FnMut(Acc, T) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| if predicate(&item) { fold(acc, item) } else { acc } +} + +fn filter_try_fold<'a, T, Acc, R: Try>( + predicate: &'a mut impl FnMut(&T) -> bool, + mut fold: impl FnMut(Acc, T) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| if predicate(&item) { fold(acc, item) } else { try { acc } } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Filter +where + P: FnMut(&I::Item) -> bool, +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + self.iter.find(&mut self.predicate) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + + // this special case allows the compiler to make `.filter(_).count()` + // branchless. Barring perfect branch prediction (which is unattainable in + // the general case), this will be much faster in >90% of cases (containing + // virtually all real workloads) and only a tiny bit slower in the rest. + // + // Having this specialization thus allows us to write `.filter(p).count()` + // where we would otherwise write `.map(|x| p(x) as usize).sum()`, which is + // less readable and also less backwards-compatible to Rust before 1.10. + // + // Using the branchless version will also simplify the LLVM byte code, thus + // leaving more budget for LLVM optimizations. + #[inline] + fn count(self) -> usize { + #[inline] + fn to_usize(mut predicate: impl FnMut(&T) -> bool) -> impl FnMut(T) -> usize { + move |x| predicate(&x) as usize + } + + self.iter.map(to_usize(self.predicate)).sum() + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_fold(init, filter_try_fold(&mut self.predicate, fold)) + } + + #[inline] + fn fold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, filter_fold(self.predicate, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Filter +where + P: FnMut(&I::Item) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option { + self.iter.rfind(&mut self.predicate) + } + + #[inline] + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_rfold(init, filter_try_fold(&mut self.predicate, fold)) + } + + #[inline] + fn rfold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, filter_fold(self.predicate, fold)) + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Filter where P: FnMut(&I::Item) -> bool {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Filter +where + P: FnMut(&I::Item) -> bool, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Filter where P: FnMut(&I::Item) -> bool {} diff --git a/library/core/src/iter/adapters/filter_map.rs b/library/core/src/iter/adapters/filter_map.rs new file mode 100644 index 0000000000000..0dccf2c533b57 --- /dev/null +++ b/library/core/src/iter/adapters/filter_map.rs @@ -0,0 +1,150 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that uses `f` to both filter and map elements from `iter`. +/// +/// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`filter_map`]: Iterator::filter_map +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct FilterMap { + iter: I, + f: F, +} +impl FilterMap { + pub(in crate::iter) fn new(iter: I, f: F) -> FilterMap { + FilterMap { iter, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for FilterMap { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("FilterMap").field("iter", &self.iter).finish() + } +} + +fn filter_map_fold( + mut f: impl FnMut(T) -> Option, + mut fold: impl FnMut(Acc, B) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| match f(item) { + Some(x) => fold(acc, x), + None => acc, + } +} + +fn filter_map_try_fold<'a, T, B, Acc, R: Try>( + f: &'a mut impl FnMut(T) -> Option, + mut fold: impl FnMut(Acc, B) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| match f(item) { + Some(x) => fold(acc, x), + None => try { acc }, + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for FilterMap +where + F: FnMut(I::Item) -> Option, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option { + self.iter.find_map(&mut self.f) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_fold(init, filter_map_try_fold(&mut self.f, fold)) + } + + #[inline] + fn fold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, filter_map_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for FilterMap +where + F: FnMut(I::Item) -> Option, +{ + #[inline] + fn next_back(&mut self) -> Option { + #[inline] + fn find( + f: &mut impl FnMut(T) -> Option, + ) -> impl FnMut((), T) -> ControlFlow + '_ { + move |(), x| match f(x) { + Some(x) => ControlFlow::Break(x), + None => ControlFlow::CONTINUE, + } + } + + self.iter.try_rfold((), find(&mut self.f)).break_value() + } + + #[inline] + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_rfold(init, filter_map_try_fold(&mut self.f, fold)) + } + + #[inline] + fn rfold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, filter_map_fold(self.f, fold)) + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for FilterMap where F: FnMut(I::Item) -> Option {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for FilterMap +where + F: FnMut(I::Item) -> Option, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for FilterMap where + F: FnMut(I::Item) -> Option +{ +} diff --git a/library/core/src/iter/adapters/flatten.rs b/library/core/src/iter/adapters/flatten.rs index 96d0a60a32768..ff85e114dc982 100644 --- a/library/core/src/iter/adapters/flatten.rs +++ b/library/core/src/iter/adapters/flatten.rs @@ -1,9 +1,7 @@ use crate::fmt; +use crate::iter::{DoubleEndedIterator, Fuse, FusedIterator, Iterator, Map}; use crate::ops::Try; -use super::super::{DoubleEndedIterator, Fuse, FusedIterator, Iterator}; -use super::Map; - /// An iterator that maps each element to an iterator, and yields the elements /// of the produced iterators. /// @@ -14,8 +12,9 @@ use super::Map; pub struct FlatMap { inner: FlattenCompat, ::IntoIter>, } + impl U> FlatMap { - pub(in super::super) fn new(iter: I, f: F) -> FlatMap { + pub(in crate::iter) fn new(iter: I, f: F) -> FlatMap { FlatMap { inner: FlattenCompat::new(iter.map(f)) } } } diff --git a/library/core/src/iter/adapters/fuse.rs b/library/core/src/iter/adapters/fuse.rs index 60ac3524e6696..ae07406531593 100644 --- a/library/core/src/iter/adapters/fuse.rs +++ b/library/core/src/iter/adapters/fuse.rs @@ -1,9 +1,6 @@ -use super::InPlaceIterable; use crate::intrinsics; -use crate::iter::adapters::zip::try_get_unchecked; -use crate::iter::adapters::SourceIter; -use crate::iter::TrustedRandomAccess; -use crate::iter::{DoubleEndedIterator, ExactSizeIterator, FusedIterator, Iterator}; +use crate::iter::adapters::{zip::try_get_unchecked, InPlaceIterable, SourceIter}; +use crate::iter::{DoubleEndedIterator, ExactSizeIterator, FusedIterator, TrustedRandomAccess}; use crate::ops::Try; /// An iterator that yields `None` forever after the underlying iterator diff --git a/library/core/src/iter/adapters/inspect.rs b/library/core/src/iter/adapters/inspect.rs new file mode 100644 index 0000000000000..88f5ee61b6b73 --- /dev/null +++ b/library/core/src/iter/adapters/inspect.rs @@ -0,0 +1,167 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::Try; + +/// An iterator that calls a function with a reference to each element before +/// yielding it. +/// +/// This `struct` is created by the [`inspect`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`inspect`]: Iterator::inspect +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct Inspect { + iter: I, + f: F, +} +impl Inspect { + pub(in crate::iter) fn new(iter: I, f: F) -> Inspect { + Inspect { iter, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for Inspect { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Inspect").field("iter", &self.iter).finish() + } +} + +impl Inspect +where + F: FnMut(&I::Item), +{ + #[inline] + fn do_inspect(&mut self, elt: Option) -> Option { + if let Some(ref a) = elt { + (self.f)(a); + } + + elt + } +} + +fn inspect_fold( + mut f: impl FnMut(&T), + mut fold: impl FnMut(Acc, T) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, item| { + f(&item); + fold(acc, item) + } +} + +fn inspect_try_fold<'a, T, Acc, R>( + f: &'a mut impl FnMut(&T), + mut fold: impl FnMut(Acc, T) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, item| { + f(&item); + fold(acc, item) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Inspect +where + F: FnMut(&I::Item), +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + let next = self.iter.next(); + self.do_inspect(next) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_fold(init, inspect_try_fold(&mut self.f, fold)) + } + + #[inline] + fn fold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, inspect_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Inspect +where + F: FnMut(&I::Item), +{ + #[inline] + fn next_back(&mut self) -> Option { + let next = self.iter.next_back(); + self.do_inspect(next) + } + + #[inline] + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_rfold(init, inspect_try_fold(&mut self.f, fold)) + } + + #[inline] + fn rfold(self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, inspect_fold(self.f, fold)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Inspect +where + F: FnMut(&I::Item), +{ + fn len(&self) -> usize { + self.iter.len() + } + + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Inspect where F: FnMut(&I::Item) {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Inspect +where + F: FnMut(&I::Item), + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Inspect where F: FnMut(&I::Item) {} diff --git a/library/core/src/iter/adapters/map.rs b/library/core/src/iter/adapters/map.rs new file mode 100644 index 0000000000000..12673806ec40d --- /dev/null +++ b/library/core/src/iter/adapters/map.rs @@ -0,0 +1,213 @@ +use crate::fmt; +use crate::iter::adapters::{zip::try_get_unchecked, SourceIter, TrustedRandomAccess}; +use crate::iter::{FusedIterator, InPlaceIterable, TrustedLen}; +use crate::ops::Try; + +/// An iterator that maps the values of `iter` with `f`. +/// +/// This `struct` is created by the [`map`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`map`]: Iterator::map +/// [`Iterator`]: trait.Iterator.html +/// +/// # Notes about side effects +/// +/// The [`map`] iterator implements [`DoubleEndedIterator`], meaning that +/// you can also [`map`] backwards: +/// +/// ```rust +/// let v: Vec = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect(); +/// +/// assert_eq!(v, [4, 3, 2]); +/// ``` +/// +/// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html +/// +/// But if your closure has state, iterating backwards may act in a way you do +/// not expect. Let's go through an example. First, in the forward direction: +/// +/// ```rust +/// let mut c = 0; +/// +/// for pair in vec!['a', 'b', 'c'].into_iter() +/// .map(|letter| { c += 1; (letter, c) }) { +/// println!("{:?}", pair); +/// } +/// ``` +/// +/// This will print "('a', 1), ('b', 2), ('c', 3)". +/// +/// Now consider this twist where we add a call to `rev`. This version will +/// print `('c', 1), ('b', 2), ('a', 3)`. Note that the letters are reversed, +/// but the values of the counter still go in order. This is because `map()` is +/// still being called lazily on each item, but we are popping items off the +/// back of the vector now, instead of shifting them from the front. +/// +/// ```rust +/// let mut c = 0; +/// +/// for pair in vec!['a', 'b', 'c'].into_iter() +/// .map(|letter| { c += 1; (letter, c) }) +/// .rev() { +/// println!("{:?}", pair); +/// } +/// ``` +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct Map { + iter: I, + f: F, +} +impl Map { + pub(in crate::iter) fn new(iter: I, f: F) -> Map { + Map { iter, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for Map { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Map").field("iter", &self.iter).finish() + } +} + +fn map_fold( + mut f: impl FnMut(T) -> B, + mut g: impl FnMut(Acc, B) -> Acc, +) -> impl FnMut(Acc, T) -> Acc { + move |acc, elt| g(acc, f(elt)) +} + +fn map_try_fold<'a, T, B, Acc, R>( + f: &'a mut impl FnMut(T) -> B, + mut g: impl FnMut(Acc, B) -> R + 'a, +) -> impl FnMut(Acc, T) -> R + 'a { + move |acc, elt| g(acc, f(elt)) +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Map +where + F: FnMut(I::Item) -> B, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option { + self.iter.next().map(&mut self.f) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + fn try_fold(&mut self, init: Acc, g: G) -> R + where + Self: Sized, + G: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_fold(init, map_try_fold(&mut self.f, g)) + } + + fn fold(self, init: Acc, g: G) -> Acc + where + G: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, map_fold(self.f, g)) + } + + unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> B + where + Self: TrustedRandomAccess, + { + // SAFETY: the caller must uphold the contract for + // `Iterator::__iterator_get_unchecked`. + unsafe { (self.f)(try_get_unchecked(&mut self.iter, idx)) } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Map +where + F: FnMut(I::Item) -> B, +{ + #[inline] + fn next_back(&mut self) -> Option { + self.iter.next_back().map(&mut self.f) + } + + fn try_rfold(&mut self, init: Acc, g: G) -> R + where + Self: Sized, + G: FnMut(Acc, Self::Item) -> R, + R: Try, + { + self.iter.try_rfold(init, map_try_fold(&mut self.f, g)) + } + + fn rfold(self, init: Acc, g: G) -> Acc + where + G: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, map_fold(self.f, g)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Map +where + F: FnMut(I::Item) -> B, +{ + fn len(&self) -> usize { + self.iter.len() + } + + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Map where F: FnMut(I::Item) -> B {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Map +where + I: TrustedLen, + F: FnMut(I::Item) -> B, +{ +} + +#[doc(hidden)] +#[unstable(feature = "trusted_random_access", issue = "none")] +unsafe impl TrustedRandomAccess for Map +where + I: TrustedRandomAccess, +{ + #[inline] + fn may_have_side_effect() -> bool { + true + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Map +where + F: FnMut(I::Item) -> B, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Map where F: FnMut(I::Item) -> B {} diff --git a/library/core/src/iter/adapters/map_while.rs b/library/core/src/iter/adapters/map_while.rs new file mode 100644 index 0000000000000..26114d5328498 --- /dev/null +++ b/library/core/src/iter/adapters/map_while.rs @@ -0,0 +1,101 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that only accepts elements while `predicate` returns `Some(_)`. +/// +/// This `struct` is created by the [`map_while`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`map_while`]: Iterator::map_while +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] +#[derive(Clone)] +pub struct MapWhile { + iter: I, + predicate: P, +} + +impl MapWhile { + pub(in crate::iter) fn new(iter: I, predicate: P) -> MapWhile { + MapWhile { iter, predicate } + } +} + +#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] +impl fmt::Debug for MapWhile { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("MapWhile").field("iter", &self.iter).finish() + } +} + +#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] +impl Iterator for MapWhile +where + P: FnMut(I::Item) -> Option, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option { + let x = self.iter.next()?; + (self.predicate)(x) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + + #[inline] + fn try_fold(&mut self, init: Acc, mut fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + let Self { iter, predicate } = self; + iter.try_fold(init, |acc, x| match predicate(x) { + Some(item) => ControlFlow::from_try(fold(acc, item)), + None => ControlFlow::Break(try { acc }), + }) + .into_try() + } + + #[inline] + fn fold(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { + move |acc, x| Ok(f(acc, x)) + } + + self.try_fold(init, ok(fold)).unwrap() + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for MapWhile +where + P: FnMut(I::Item) -> Option, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for MapWhile where + P: FnMut(I::Item) -> Option +{ +} diff --git a/library/core/src/iter/adapters/mod.rs b/library/core/src/iter/adapters/mod.rs index 9586284e1d706..5ef5717085e4f 100644 --- a/library/core/src/iter/adapters/mod.rs +++ b/library/core/src/iter/adapters/mod.rs @@ -1,26 +1,51 @@ -use crate::cmp; -use crate::fmt; -use crate::intrinsics; -use crate::ops::{Add, AddAssign, ControlFlow, Try}; - -use super::from_fn; -use super::{ - DoubleEndedIterator, ExactSizeIterator, FusedIterator, InPlaceIterable, Iterator, TrustedLen, -}; +use crate::iter::{InPlaceIterable, Iterator}; +use crate::ops::{ControlFlow, Try}; mod chain; +mod cloned; +mod copied; +mod cycle; +mod enumerate; +mod filter; +mod filter_map; mod flatten; mod fuse; +mod inspect; +mod map; +mod map_while; +mod peekable; +mod rev; +mod scan; +mod skip; +mod skip_while; +mod step_by; +mod take; +mod take_while; mod zip; -pub use self::chain::Chain; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::flatten::{FlatMap, Flatten}; -pub use self::fuse::Fuse; -use self::zip::try_get_unchecked; +pub use self::{ + chain::Chain, cycle::Cycle, enumerate::Enumerate, filter::Filter, filter_map::FilterMap, + flatten::FlatMap, fuse::Fuse, inspect::Inspect, map::Map, peekable::Peekable, rev::Rev, + scan::Scan, skip::Skip, skip_while::SkipWhile, take::Take, take_while::TakeWhile, zip::Zip, +}; + +#[stable(feature = "iter_cloned", since = "1.1.0")] +pub use self::cloned::Cloned; + +#[stable(feature = "iterator_step_by", since = "1.28.0")] +pub use self::step_by::StepBy; + +#[stable(feature = "iterator_flatten", since = "1.29.0")] +pub use self::flatten::Flatten; + +#[stable(feature = "iter_copied", since = "1.36.0")] +pub use self::copied::Copied; + +#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] +pub use self::map_while::MapWhile; + #[unstable(feature = "trusted_random_access", issue = "none")] pub use self::zip::TrustedRandomAccess; -pub use self::zip::Zip; /// This trait provides transitive access to source-stage in an interator-adapter pipeline /// under the conditions that @@ -89,2810 +114,6 @@ pub unsafe trait SourceIter { unsafe fn as_inner(&mut self) -> &mut Self::Source; } -/// A double-ended iterator with the direction inverted. -/// -/// This `struct` is created by the [`rev`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`rev`]: Iterator::rev -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Rev { - iter: T, -} -impl Rev { - pub(super) fn new(iter: T) -> Rev { - Rev { iter } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Rev -where - I: DoubleEndedIterator, -{ - type Item = ::Item; - - #[inline] - fn next(&mut self) -> Option<::Item> { - self.iter.next_back() - } - #[inline] - fn size_hint(&self) -> (usize, Option) { - self.iter.size_hint() - } - - #[inline] - fn advance_by(&mut self, n: usize) -> Result<(), usize> { - self.iter.advance_back_by(n) - } - - #[inline] - fn nth(&mut self, n: usize) -> Option<::Item> { - self.iter.nth_back(n) - } - - fn try_fold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.iter.try_rfold(init, f) - } - - fn fold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.rfold(init, f) - } - - #[inline] - fn find

(&mut self, predicate: P) -> Option - where - P: FnMut(&Self::Item) -> bool, - { - self.iter.rfind(predicate) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Rev -where - I: DoubleEndedIterator, -{ - #[inline] - fn next_back(&mut self) -> Option<::Item> { - self.iter.next() - } - - #[inline] - fn advance_back_by(&mut self, n: usize) -> Result<(), usize> { - self.iter.advance_by(n) - } - - #[inline] - fn nth_back(&mut self, n: usize) -> Option<::Item> { - self.iter.nth(n) - } - - fn try_rfold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.iter.try_fold(init, f) - } - - fn rfold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.fold(init, f) - } - - fn rfind

(&mut self, predicate: P) -> Option - where - P: FnMut(&Self::Item) -> bool, - { - self.iter.find(predicate) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Rev -where - I: ExactSizeIterator + DoubleEndedIterator, -{ - fn len(&self) -> usize { - self.iter.len() - } - - fn is_empty(&self) -> bool { - self.iter.is_empty() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Rev where I: FusedIterator + DoubleEndedIterator {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Rev where I: TrustedLen + DoubleEndedIterator {} - -/// An iterator that copies the elements of an underlying iterator. -/// -/// This `struct` is created by the [`copied`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`copied`]: Iterator::copied -/// [`Iterator`]: trait.Iterator.html -#[stable(feature = "iter_copied", since = "1.36.0")] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[derive(Clone, Debug)] -pub struct Copied { - it: I, -} - -impl Copied { - pub(super) fn new(it: I) -> Copied { - Copied { it } - } -} - -fn copy_fold(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, &T) -> Acc { - move |acc, &elt| f(acc, elt) -} - -fn copy_try_fold(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R { - move |acc, &elt| f(acc, elt) -} - -#[stable(feature = "iter_copied", since = "1.36.0")] -impl<'a, I, T: 'a> Iterator for Copied -where - I: Iterator, - T: Copy, -{ - type Item = T; - - fn next(&mut self) -> Option { - self.it.next().copied() - } - - fn size_hint(&self) -> (usize, Option) { - self.it.size_hint() - } - - fn try_fold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.it.try_fold(init, copy_try_fold(f)) - } - - fn fold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.it.fold(init, copy_fold(f)) - } - - fn nth(&mut self, n: usize) -> Option { - self.it.nth(n).copied() - } - - fn last(self) -> Option { - self.it.last().copied() - } - - fn count(self) -> usize { - self.it.count() - } - - unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T - where - Self: TrustedRandomAccess, - { - // SAFETY: the caller must uphold the contract for - // `Iterator::__iterator_get_unchecked`. - *unsafe { try_get_unchecked(&mut self.it, idx) } - } -} - -#[stable(feature = "iter_copied", since = "1.36.0")] -impl<'a, I, T: 'a> DoubleEndedIterator for Copied -where - I: DoubleEndedIterator, - T: Copy, -{ - fn next_back(&mut self) -> Option { - self.it.next_back().copied() - } - - fn try_rfold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.it.try_rfold(init, copy_try_fold(f)) - } - - fn rfold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.it.rfold(init, copy_fold(f)) - } -} - -#[stable(feature = "iter_copied", since = "1.36.0")] -impl<'a, I, T: 'a> ExactSizeIterator for Copied -where - I: ExactSizeIterator, - T: Copy, -{ - fn len(&self) -> usize { - self.it.len() - } - - fn is_empty(&self) -> bool { - self.it.is_empty() - } -} - -#[stable(feature = "iter_copied", since = "1.36.0")] -impl<'a, I, T: 'a> FusedIterator for Copied -where - I: FusedIterator, - T: Copy, -{ -} - -#[doc(hidden)] -#[unstable(feature = "trusted_random_access", issue = "none")] -unsafe impl TrustedRandomAccess for Copied -where - I: TrustedRandomAccess, -{ - #[inline] - fn may_have_side_effect() -> bool { - I::may_have_side_effect() - } -} - -#[stable(feature = "iter_copied", since = "1.36.0")] -unsafe impl<'a, I, T: 'a> TrustedLen for Copied -where - I: TrustedLen, - T: Copy, -{ -} - -/// An iterator that clones the elements of an underlying iterator. -/// -/// This `struct` is created by the [`cloned`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`cloned`]: Iterator::cloned -/// [`Iterator`]: trait.Iterator.html -#[stable(feature = "iter_cloned", since = "1.1.0")] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[derive(Clone, Debug)] -pub struct Cloned { - it: I, -} -impl Cloned { - pub(super) fn new(it: I) -> Cloned { - Cloned { it } - } -} - -fn clone_try_fold(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R { - move |acc, elt| f(acc, elt.clone()) -} - -#[stable(feature = "iter_cloned", since = "1.1.0")] -impl<'a, I, T: 'a> Iterator for Cloned -where - I: Iterator, - T: Clone, -{ - type Item = T; - - fn next(&mut self) -> Option { - self.it.next().cloned() - } - - fn size_hint(&self) -> (usize, Option) { - self.it.size_hint() - } - - fn try_fold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.it.try_fold(init, clone_try_fold(f)) - } - - fn fold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.it.map(T::clone).fold(init, f) - } - - unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T - where - Self: TrustedRandomAccess, - { - // SAFETY: the caller must uphold the contract for - // `Iterator::__iterator_get_unchecked`. - unsafe { try_get_unchecked(&mut self.it, idx).clone() } - } -} - -#[stable(feature = "iter_cloned", since = "1.1.0")] -impl<'a, I, T: 'a> DoubleEndedIterator for Cloned -where - I: DoubleEndedIterator, - T: Clone, -{ - fn next_back(&mut self) -> Option { - self.it.next_back().cloned() - } - - fn try_rfold(&mut self, init: B, f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - self.it.try_rfold(init, clone_try_fold(f)) - } - - fn rfold(self, init: Acc, f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - self.it.map(T::clone).rfold(init, f) - } -} - -#[stable(feature = "iter_cloned", since = "1.1.0")] -impl<'a, I, T: 'a> ExactSizeIterator for Cloned -where - I: ExactSizeIterator, - T: Clone, -{ - fn len(&self) -> usize { - self.it.len() - } - - fn is_empty(&self) -> bool { - self.it.is_empty() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl<'a, I, T: 'a> FusedIterator for Cloned -where - I: FusedIterator, - T: Clone, -{ -} - -#[doc(hidden)] -#[unstable(feature = "trusted_random_access", issue = "none")] -unsafe impl TrustedRandomAccess for Cloned -where - I: TrustedRandomAccess, -{ - #[inline] - fn may_have_side_effect() -> bool { - true - } -} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl<'a, I, T: 'a> TrustedLen for Cloned -where - I: TrustedLen, - T: Clone, -{ -} - -/// An iterator that repeats endlessly. -/// -/// This `struct` is created by the [`cycle`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`cycle`]: Iterator::cycle -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Cycle { - orig: I, - iter: I, -} -impl Cycle { - pub(super) fn new(iter: I) -> Cycle { - Cycle { orig: iter.clone(), iter } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Cycle -where - I: Clone + Iterator, -{ - type Item = ::Item; - - #[inline] - fn next(&mut self) -> Option<::Item> { - match self.iter.next() { - None => { - self.iter = self.orig.clone(); - self.iter.next() - } - y => y, - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - // the cycle iterator is either empty or infinite - match self.orig.size_hint() { - sz @ (0, Some(0)) => sz, - (0, _) => (0, None), - _ => (usize::MAX, None), - } - } - - #[inline] - fn try_fold(&mut self, mut acc: Acc, mut f: F) -> R - where - F: FnMut(Acc, Self::Item) -> R, - R: Try, - { - // fully iterate the current iterator. this is necessary because - // `self.iter` may be empty even when `self.orig` isn't - acc = self.iter.try_fold(acc, &mut f)?; - self.iter = self.orig.clone(); - - // complete a full cycle, keeping track of whether the cycled - // iterator is empty or not. we need to return early in case - // of an empty iterator to prevent an infinite loop - let mut is_empty = true; - acc = self.iter.try_fold(acc, |acc, x| { - is_empty = false; - f(acc, x) - })?; - - if is_empty { - return try { acc }; - } - - loop { - self.iter = self.orig.clone(); - acc = self.iter.try_fold(acc, &mut f)?; - } - } - - // No `fold` override, because `fold` doesn't make much sense for `Cycle`, - // and we can't do anything better than the default. -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Cycle where I: Clone + Iterator {} - -/// An iterator for stepping iterators by a custom amount. -/// -/// This `struct` is created by the [`step_by`] method on [`Iterator`]. See -/// its documentation for more. -/// -/// [`step_by`]: Iterator::step_by -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "iterator_step_by", since = "1.28.0")] -#[derive(Clone, Debug)] -pub struct StepBy { - iter: I, - step: usize, - first_take: bool, -} -impl StepBy { - pub(super) fn new(iter: I, step: usize) -> StepBy { - assert!(step != 0); - StepBy { iter, step: step - 1, first_take: true } - } -} - -#[stable(feature = "iterator_step_by", since = "1.28.0")] -impl Iterator for StepBy -where - I: Iterator, -{ - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - if self.first_take { - self.first_take = false; - self.iter.next() - } else { - self.iter.nth(self.step) - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - #[inline] - fn first_size(step: usize) -> impl Fn(usize) -> usize { - move |n| if n == 0 { 0 } else { 1 + (n - 1) / (step + 1) } - } - - #[inline] - fn other_size(step: usize) -> impl Fn(usize) -> usize { - move |n| n / (step + 1) - } - - let (low, high) = self.iter.size_hint(); - - if self.first_take { - let f = first_size(self.step); - (f(low), high.map(f)) - } else { - let f = other_size(self.step); - (f(low), high.map(f)) - } - } - - #[inline] - fn nth(&mut self, mut n: usize) -> Option { - if self.first_take { - self.first_take = false; - let first = self.iter.next(); - if n == 0 { - return first; - } - n -= 1; - } - // n and self.step are indices, we need to add 1 to get the amount of elements - // When calling `.nth`, we need to subtract 1 again to convert back to an index - // step + 1 can't overflow because `.step_by` sets `self.step` to `step - 1` - let mut step = self.step + 1; - // n + 1 could overflow - // thus, if n is usize::MAX, instead of adding one, we call .nth(step) - if n == usize::MAX { - self.iter.nth(step - 1); - } else { - n += 1; - } - - // overflow handling - loop { - let mul = n.checked_mul(step); - { - if intrinsics::likely(mul.is_some()) { - return self.iter.nth(mul.unwrap() - 1); - } - } - let div_n = usize::MAX / n; - let div_step = usize::MAX / step; - let nth_n = div_n * n; - let nth_step = div_step * step; - let nth = if nth_n > nth_step { - step -= div_n; - nth_n - } else { - n -= div_step; - nth_step - }; - self.iter.nth(nth - 1); - } - } - - fn try_fold(&mut self, mut acc: Acc, mut f: F) -> R - where - F: FnMut(Acc, Self::Item) -> R, - R: Try, - { - #[inline] - fn nth(iter: &mut I, step: usize) -> impl FnMut() -> Option + '_ { - move || iter.nth(step) - } - - if self.first_take { - self.first_take = false; - match self.iter.next() { - None => return try { acc }, - Some(x) => acc = f(acc, x)?, - } - } - from_fn(nth(&mut self.iter, self.step)).try_fold(acc, f) - } - - fn fold(mut self, mut acc: Acc, mut f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn nth(iter: &mut I, step: usize) -> impl FnMut() -> Option + '_ { - move || iter.nth(step) - } - - if self.first_take { - self.first_take = false; - match self.iter.next() { - None => return acc, - Some(x) => acc = f(acc, x), - } - } - from_fn(nth(&mut self.iter, self.step)).fold(acc, f) - } -} - -impl StepBy -where - I: ExactSizeIterator, -{ - // The zero-based index starting from the end of the iterator of the - // last element. Used in the `DoubleEndedIterator` implementation. - fn next_back_index(&self) -> usize { - let rem = self.iter.len() % (self.step + 1); - if self.first_take { - if rem == 0 { self.step } else { rem - 1 } - } else { - rem - } - } -} - -#[stable(feature = "double_ended_step_by_iterator", since = "1.38.0")] -impl DoubleEndedIterator for StepBy -where - I: DoubleEndedIterator + ExactSizeIterator, -{ - #[inline] - fn next_back(&mut self) -> Option { - self.iter.nth_back(self.next_back_index()) - } - - #[inline] - fn nth_back(&mut self, n: usize) -> Option { - // `self.iter.nth_back(usize::MAX)` does the right thing here when `n` - // is out of bounds because the length of `self.iter` does not exceed - // `usize::MAX` (because `I: ExactSizeIterator`) and `nth_back` is - // zero-indexed - let n = n.saturating_mul(self.step + 1).saturating_add(self.next_back_index()); - self.iter.nth_back(n) - } - - fn try_rfold(&mut self, init: Acc, mut f: F) -> R - where - F: FnMut(Acc, Self::Item) -> R, - R: Try, - { - #[inline] - fn nth_back( - iter: &mut I, - step: usize, - ) -> impl FnMut() -> Option + '_ { - move || iter.nth_back(step) - } - - match self.next_back() { - None => try { init }, - Some(x) => { - let acc = f(init, x)?; - from_fn(nth_back(&mut self.iter, self.step)).try_fold(acc, f) - } - } - } - - #[inline] - fn rfold(mut self, init: Acc, mut f: F) -> Acc - where - Self: Sized, - F: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn nth_back( - iter: &mut I, - step: usize, - ) -> impl FnMut() -> Option + '_ { - move || iter.nth_back(step) - } - - match self.next_back() { - None => init, - Some(x) => { - let acc = f(init, x); - from_fn(nth_back(&mut self.iter, self.step)).fold(acc, f) - } - } - } -} - -// StepBy can only make the iterator shorter, so the len will still fit. -#[stable(feature = "iterator_step_by", since = "1.28.0")] -impl ExactSizeIterator for StepBy where I: ExactSizeIterator {} - -/// An iterator that maps the values of `iter` with `f`. -/// -/// This `struct` is created by the [`map`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`map`]: Iterator::map -/// [`Iterator`]: trait.Iterator.html -/// -/// # Notes about side effects -/// -/// The [`map`] iterator implements [`DoubleEndedIterator`], meaning that -/// you can also [`map`] backwards: -/// -/// ```rust -/// let v: Vec = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect(); -/// -/// assert_eq!(v, [4, 3, 2]); -/// ``` -/// -/// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html -/// -/// But if your closure has state, iterating backwards may act in a way you do -/// not expect. Let's go through an example. First, in the forward direction: -/// -/// ```rust -/// let mut c = 0; -/// -/// for pair in vec!['a', 'b', 'c'].into_iter() -/// .map(|letter| { c += 1; (letter, c) }) { -/// println!("{:?}", pair); -/// } -/// ``` -/// -/// This will print "('a', 1), ('b', 2), ('c', 3)". -/// -/// Now consider this twist where we add a call to `rev`. This version will -/// print `('c', 1), ('b', 2), ('a', 3)`. Note that the letters are reversed, -/// but the values of the counter still go in order. This is because `map()` is -/// still being called lazily on each item, but we are popping items off the -/// back of the vector now, instead of shifting them from the front. -/// -/// ```rust -/// let mut c = 0; -/// -/// for pair in vec!['a', 'b', 'c'].into_iter() -/// .map(|letter| { c += 1; (letter, c) }) -/// .rev() { -/// println!("{:?}", pair); -/// } -/// ``` -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct Map { - iter: I, - f: F, -} -impl Map { - pub(super) fn new(iter: I, f: F) -> Map { - Map { iter, f } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for Map { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Map").field("iter", &self.iter).finish() - } -} - -fn map_fold( - mut f: impl FnMut(T) -> B, - mut g: impl FnMut(Acc, B) -> Acc, -) -> impl FnMut(Acc, T) -> Acc { - move |acc, elt| g(acc, f(elt)) -} - -fn map_try_fold<'a, T, B, Acc, R>( - f: &'a mut impl FnMut(T) -> B, - mut g: impl FnMut(Acc, B) -> R + 'a, -) -> impl FnMut(Acc, T) -> R + 'a { - move |acc, elt| g(acc, f(elt)) -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Map -where - F: FnMut(I::Item) -> B, -{ - type Item = B; - - #[inline] - fn next(&mut self) -> Option { - self.iter.next().map(&mut self.f) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - self.iter.size_hint() - } - - fn try_fold(&mut self, init: Acc, g: G) -> R - where - Self: Sized, - G: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_fold(init, map_try_fold(&mut self.f, g)) - } - - fn fold(self, init: Acc, g: G) -> Acc - where - G: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.fold(init, map_fold(self.f, g)) - } - - unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> B - where - Self: TrustedRandomAccess, - { - // SAFETY: the caller must uphold the contract for - // `Iterator::__iterator_get_unchecked`. - unsafe { (self.f)(try_get_unchecked(&mut self.iter, idx)) } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Map -where - F: FnMut(I::Item) -> B, -{ - #[inline] - fn next_back(&mut self) -> Option { - self.iter.next_back().map(&mut self.f) - } - - fn try_rfold(&mut self, init: Acc, g: G) -> R - where - Self: Sized, - G: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_rfold(init, map_try_fold(&mut self.f, g)) - } - - fn rfold(self, init: Acc, g: G) -> Acc - where - G: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.rfold(init, map_fold(self.f, g)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Map -where - F: FnMut(I::Item) -> B, -{ - fn len(&self) -> usize { - self.iter.len() - } - - fn is_empty(&self) -> bool { - self.iter.is_empty() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Map where F: FnMut(I::Item) -> B {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Map -where - I: TrustedLen, - F: FnMut(I::Item) -> B, -{ -} - -#[doc(hidden)] -#[unstable(feature = "trusted_random_access", issue = "none")] -unsafe impl TrustedRandomAccess for Map -where - I: TrustedRandomAccess, -{ - #[inline] - fn may_have_side_effect() -> bool { - true - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Map -where - F: FnMut(I::Item) -> B, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Map where F: FnMut(I::Item) -> B {} - -/// An iterator that filters the elements of `iter` with `predicate`. -/// -/// This `struct` is created by the [`filter`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`filter`]: Iterator::filter -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct Filter { - iter: I, - predicate: P, -} -impl Filter { - pub(super) fn new(iter: I, predicate: P) -> Filter { - Filter { iter, predicate } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for Filter { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Filter").field("iter", &self.iter).finish() - } -} - -fn filter_fold( - mut predicate: impl FnMut(&T) -> bool, - mut fold: impl FnMut(Acc, T) -> Acc, -) -> impl FnMut(Acc, T) -> Acc { - move |acc, item| if predicate(&item) { fold(acc, item) } else { acc } -} - -fn filter_try_fold<'a, T, Acc, R: Try>( - predicate: &'a mut impl FnMut(&T) -> bool, - mut fold: impl FnMut(Acc, T) -> R + 'a, -) -> impl FnMut(Acc, T) -> R + 'a { - move |acc, item| if predicate(&item) { fold(acc, item) } else { try { acc } } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Filter -where - P: FnMut(&I::Item) -> bool, -{ - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - self.iter.find(&mut self.predicate) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the predicate - } - - // this special case allows the compiler to make `.filter(_).count()` - // branchless. Barring perfect branch prediction (which is unattainable in - // the general case), this will be much faster in >90% of cases (containing - // virtually all real workloads) and only a tiny bit slower in the rest. - // - // Having this specialization thus allows us to write `.filter(p).count()` - // where we would otherwise write `.map(|x| p(x) as usize).sum()`, which is - // less readable and also less backwards-compatible to Rust before 1.10. - // - // Using the branchless version will also simplify the LLVM byte code, thus - // leaving more budget for LLVM optimizations. - #[inline] - fn count(self) -> usize { - #[inline] - fn to_usize(mut predicate: impl FnMut(&T) -> bool) -> impl FnMut(T) -> usize { - move |x| predicate(&x) as usize - } - - self.iter.map(to_usize(self.predicate)).sum() - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_fold(init, filter_try_fold(&mut self.predicate, fold)) - } - - #[inline] - fn fold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.fold(init, filter_fold(self.predicate, fold)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Filter -where - P: FnMut(&I::Item) -> bool, -{ - #[inline] - fn next_back(&mut self) -> Option { - self.iter.rfind(&mut self.predicate) - } - - #[inline] - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_rfold(init, filter_try_fold(&mut self.predicate, fold)) - } - - #[inline] - fn rfold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.rfold(init, filter_fold(self.predicate, fold)) - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Filter where P: FnMut(&I::Item) -> bool {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Filter -where - P: FnMut(&I::Item) -> bool, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Filter where P: FnMut(&I::Item) -> bool {} - -/// An iterator that uses `f` to both filter and map elements from `iter`. -/// -/// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`filter_map`]: Iterator::filter_map -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct FilterMap { - iter: I, - f: F, -} -impl FilterMap { - pub(super) fn new(iter: I, f: F) -> FilterMap { - FilterMap { iter, f } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for FilterMap { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("FilterMap").field("iter", &self.iter).finish() - } -} - -fn filter_map_fold( - mut f: impl FnMut(T) -> Option, - mut fold: impl FnMut(Acc, B) -> Acc, -) -> impl FnMut(Acc, T) -> Acc { - move |acc, item| match f(item) { - Some(x) => fold(acc, x), - None => acc, - } -} - -fn filter_map_try_fold<'a, T, B, Acc, R: Try>( - f: &'a mut impl FnMut(T) -> Option, - mut fold: impl FnMut(Acc, B) -> R + 'a, -) -> impl FnMut(Acc, T) -> R + 'a { - move |acc, item| match f(item) { - Some(x) => fold(acc, x), - None => try { acc }, - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for FilterMap -where - F: FnMut(I::Item) -> Option, -{ - type Item = B; - - #[inline] - fn next(&mut self) -> Option { - self.iter.find_map(&mut self.f) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the predicate - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_fold(init, filter_map_try_fold(&mut self.f, fold)) - } - - #[inline] - fn fold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.fold(init, filter_map_fold(self.f, fold)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for FilterMap -where - F: FnMut(I::Item) -> Option, -{ - #[inline] - fn next_back(&mut self) -> Option { - #[inline] - fn find( - f: &mut impl FnMut(T) -> Option, - ) -> impl FnMut((), T) -> ControlFlow + '_ { - move |(), x| match f(x) { - Some(x) => ControlFlow::Break(x), - None => ControlFlow::CONTINUE, - } - } - - self.iter.try_rfold((), find(&mut self.f)).break_value() - } - - #[inline] - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_rfold(init, filter_map_try_fold(&mut self.f, fold)) - } - - #[inline] - fn rfold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.rfold(init, filter_map_fold(self.f, fold)) - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for FilterMap where F: FnMut(I::Item) -> Option {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for FilterMap -where - F: FnMut(I::Item) -> Option, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for FilterMap where - F: FnMut(I::Item) -> Option -{ -} - -/// An iterator that yields the current count and the element during iteration. -/// -/// This `struct` is created by the [`enumerate`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`enumerate`]: Iterator::enumerate -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Enumerate { - iter: I, - count: usize, -} -impl Enumerate { - pub(super) fn new(iter: I) -> Enumerate { - Enumerate { iter, count: 0 } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Enumerate -where - I: Iterator, -{ - type Item = (usize, ::Item); - - /// # Overflow Behavior - /// - /// The method does no guarding against overflows, so enumerating more than - /// `usize::MAX` elements either produces the wrong result or panics. If - /// debug assertions are enabled, a panic is guaranteed. - /// - /// # Panics - /// - /// Might panic if the index of the element overflows a `usize`. - #[inline] - fn next(&mut self) -> Option<(usize, ::Item)> { - let a = self.iter.next()?; - let i = self.count; - // Possible undefined overflow. - AddAssign::add_assign(&mut self.count, 1); - Some((i, a)) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - self.iter.size_hint() - } - - #[inline] - fn nth(&mut self, n: usize) -> Option<(usize, I::Item)> { - let a = self.iter.nth(n)?; - // Possible undefined overflow. - let i = Add::add(self.count, n); - self.count = Add::add(i, 1); - Some((i, a)) - } - - #[inline] - fn count(self) -> usize { - self.iter.count() - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - #[inline] - fn enumerate<'a, T, Acc, R>( - count: &'a mut usize, - mut fold: impl FnMut(Acc, (usize, T)) -> R + 'a, - ) -> impl FnMut(Acc, T) -> R + 'a { - move |acc, item| { - let acc = fold(acc, (*count, item)); - // Possible undefined overflow. - AddAssign::add_assign(count, 1); - acc - } - } - - self.iter.try_fold(init, enumerate(&mut self.count, fold)) - } - - #[inline] - fn fold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn enumerate( - mut count: usize, - mut fold: impl FnMut(Acc, (usize, T)) -> Acc, - ) -> impl FnMut(Acc, T) -> Acc { - move |acc, item| { - let acc = fold(acc, (count, item)); - // Possible undefined overflow. - AddAssign::add_assign(&mut count, 1); - acc - } - } - - self.iter.fold(init, enumerate(self.count, fold)) - } - - unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> ::Item - where - Self: TrustedRandomAccess, - { - // SAFETY: the caller must uphold the contract for - // `Iterator::__iterator_get_unchecked`. - let value = unsafe { try_get_unchecked(&mut self.iter, idx) }; - (Add::add(self.count, idx), value) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Enumerate -where - I: ExactSizeIterator + DoubleEndedIterator, -{ - #[inline] - fn next_back(&mut self) -> Option<(usize, ::Item)> { - let a = self.iter.next_back()?; - let len = self.iter.len(); - // Can safely add, `ExactSizeIterator` promises that the number of - // elements fits into a `usize`. - Some((self.count + len, a)) - } - - #[inline] - fn nth_back(&mut self, n: usize) -> Option<(usize, ::Item)> { - let a = self.iter.nth_back(n)?; - let len = self.iter.len(); - // Can safely add, `ExactSizeIterator` promises that the number of - // elements fits into a `usize`. - Some((self.count + len, a)) - } - - #[inline] - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - // Can safely add and subtract the count, as `ExactSizeIterator` promises - // that the number of elements fits into a `usize`. - fn enumerate( - mut count: usize, - mut fold: impl FnMut(Acc, (usize, T)) -> R, - ) -> impl FnMut(Acc, T) -> R { - move |acc, item| { - count -= 1; - fold(acc, (count, item)) - } - } - - let count = self.count + self.iter.len(); - self.iter.try_rfold(init, enumerate(count, fold)) - } - - #[inline] - fn rfold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - // Can safely add and subtract the count, as `ExactSizeIterator` promises - // that the number of elements fits into a `usize`. - fn enumerate( - mut count: usize, - mut fold: impl FnMut(Acc, (usize, T)) -> Acc, - ) -> impl FnMut(Acc, T) -> Acc { - move |acc, item| { - count -= 1; - fold(acc, (count, item)) - } - } - - let count = self.count + self.iter.len(); - self.iter.rfold(init, enumerate(count, fold)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Enumerate -where - I: ExactSizeIterator, -{ - fn len(&self) -> usize { - self.iter.len() - } - - fn is_empty(&self) -> bool { - self.iter.is_empty() - } -} - -#[doc(hidden)] -#[unstable(feature = "trusted_random_access", issue = "none")] -unsafe impl TrustedRandomAccess for Enumerate -where - I: TrustedRandomAccess, -{ - fn may_have_side_effect() -> bool { - I::may_have_side_effect() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Enumerate where I: FusedIterator {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Enumerate where I: TrustedLen {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Enumerate -where - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Enumerate {} - -/// An iterator with a `peek()` that returns an optional reference to the next -/// element. -/// -/// This `struct` is created by the [`peekable`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`peekable`]: Iterator::peekable -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Peekable { - iter: I, - /// Remember a peeked value, even if it was None. - peeked: Option>, -} -impl Peekable { - pub(super) fn new(iter: I) -> Peekable { - Peekable { iter, peeked: None } - } -} - -// Peekable must remember if a None has been seen in the `.peek()` method. -// It ensures that `.peek(); .peek();` or `.peek(); .next();` only advances the -// underlying iterator at most once. This does not by itself make the iterator -// fused. -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Peekable { - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - match self.peeked.take() { - Some(v) => v, - None => self.iter.next(), - } - } - - #[inline] - #[rustc_inherit_overflow_checks] - fn count(mut self) -> usize { - match self.peeked.take() { - Some(None) => 0, - Some(Some(_)) => 1 + self.iter.count(), - None => self.iter.count(), - } - } - - #[inline] - fn nth(&mut self, n: usize) -> Option { - match self.peeked.take() { - Some(None) => None, - Some(v @ Some(_)) if n == 0 => v, - Some(Some(_)) => self.iter.nth(n - 1), - None => self.iter.nth(n), - } - } - - #[inline] - fn last(mut self) -> Option { - let peek_opt = match self.peeked.take() { - Some(None) => return None, - Some(v) => v, - None => None, - }; - self.iter.last().or(peek_opt) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let peek_len = match self.peeked { - Some(None) => return (0, Some(0)), - Some(Some(_)) => 1, - None => 0, - }; - let (lo, hi) = self.iter.size_hint(); - let lo = lo.saturating_add(peek_len); - let hi = match hi { - Some(x) => x.checked_add(peek_len), - None => None, - }; - (lo, hi) - } - - #[inline] - fn try_fold(&mut self, init: B, mut f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - let acc = match self.peeked.take() { - Some(None) => return try { init }, - Some(Some(v)) => f(init, v)?, - None => init, - }; - self.iter.try_fold(acc, f) - } - - #[inline] - fn fold(self, init: Acc, mut fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - let acc = match self.peeked { - Some(None) => return init, - Some(Some(v)) => fold(init, v), - None => init, - }; - self.iter.fold(acc, fold) - } -} - -#[stable(feature = "double_ended_peek_iterator", since = "1.38.0")] -impl DoubleEndedIterator for Peekable -where - I: DoubleEndedIterator, -{ - #[inline] - fn next_back(&mut self) -> Option { - match self.peeked.as_mut() { - Some(v @ Some(_)) => self.iter.next_back().or_else(|| v.take()), - Some(None) => None, - None => self.iter.next_back(), - } - } - - #[inline] - fn try_rfold(&mut self, init: B, mut f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - match self.peeked.take() { - Some(None) => try { init }, - Some(Some(v)) => match self.iter.try_rfold(init, &mut f).into_result() { - Ok(acc) => f(acc, v), - Err(e) => { - self.peeked = Some(Some(v)); - Try::from_error(e) - } - }, - None => self.iter.try_rfold(init, f), - } - } - - #[inline] - fn rfold(self, init: Acc, mut fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - match self.peeked { - Some(None) => init, - Some(Some(v)) => { - let acc = self.iter.rfold(init, &mut fold); - fold(acc, v) - } - None => self.iter.rfold(init, fold), - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Peekable {} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Peekable {} - -impl Peekable { - /// Returns a reference to the next() value without advancing the iterator. - /// - /// Like [`next`], if there is a value, it is wrapped in a `Some(T)`. - /// But if the iteration is over, `None` is returned. - /// - /// [`next`]: Iterator::next - /// - /// Because `peek()` returns a reference, and many iterators iterate over - /// references, there can be a possibly confusing situation where the - /// return value is a double reference. You can see this effect in the - /// examples below. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// let xs = [1, 2, 3]; - /// - /// let mut iter = xs.iter().peekable(); - /// - /// // peek() lets us see into the future - /// assert_eq!(iter.peek(), Some(&&1)); - /// assert_eq!(iter.next(), Some(&1)); - /// - /// assert_eq!(iter.next(), Some(&2)); - /// - /// // The iterator does not advance even if we `peek` multiple times - /// assert_eq!(iter.peek(), Some(&&3)); - /// assert_eq!(iter.peek(), Some(&&3)); - /// - /// assert_eq!(iter.next(), Some(&3)); - /// - /// // After the iterator is finished, so is `peek()` - /// assert_eq!(iter.peek(), None); - /// assert_eq!(iter.next(), None); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn peek(&mut self) -> Option<&I::Item> { - let iter = &mut self.iter; - self.peeked.get_or_insert_with(|| iter.next()).as_ref() - } - - /// Consume and return the next value of this iterator if a condition is true. - /// - /// If `func` returns `true` for the next value of this iterator, consume and return it. - /// Otherwise, return `None`. - /// - /// # Examples - /// Consume a number if it's equal to 0. - /// ``` - /// #![feature(peekable_next_if)] - /// let mut iter = (0..5).peekable(); - /// // The first item of the iterator is 0; consume it. - /// assert_eq!(iter.next_if(|&x| x == 0), Some(0)); - /// // The next item returned is now 1, so `consume` will return `false`. - /// assert_eq!(iter.next_if(|&x| x == 0), None); - /// // `next_if` saves the value of the next item if it was not equal to `expected`. - /// assert_eq!(iter.next(), Some(1)); - /// ``` - /// - /// Consume any number less than 10. - /// ``` - /// #![feature(peekable_next_if)] - /// let mut iter = (1..20).peekable(); - /// // Consume all numbers less than 10 - /// while iter.next_if(|&x| x < 10).is_some() {} - /// // The next value returned will be 10 - /// assert_eq!(iter.next(), Some(10)); - /// ``` - #[unstable(feature = "peekable_next_if", issue = "72480")] - pub fn next_if(&mut self, func: impl FnOnce(&I::Item) -> bool) -> Option { - match self.next() { - Some(matched) if func(&matched) => Some(matched), - other => { - // Since we called `self.next()`, we consumed `self.peeked`. - assert!(self.peeked.is_none()); - self.peeked = Some(other); - None - } - } - } - - /// Consume and return the next item if it is equal to `expected`. - /// - /// # Example - /// Consume a number if it's equal to 0. - /// ``` - /// #![feature(peekable_next_if)] - /// let mut iter = (0..5).peekable(); - /// // The first item of the iterator is 0; consume it. - /// assert_eq!(iter.next_if_eq(&0), Some(0)); - /// // The next item returned is now 1, so `consume` will return `false`. - /// assert_eq!(iter.next_if_eq(&0), None); - /// // `next_if_eq` saves the value of the next item if it was not equal to `expected`. - /// assert_eq!(iter.next(), Some(1)); - /// ``` - #[unstable(feature = "peekable_next_if", issue = "72480")] - pub fn next_if_eq(&mut self, expected: &T) -> Option - where - T: ?Sized, - I::Item: PartialEq, - { - self.next_if(|next| next == expected) - } -} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Peekable where I: TrustedLen {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Peekable -where - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Peekable {} - -/// An iterator that rejects elements while `predicate` returns `true`. -/// -/// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`skip_while`]: Iterator::skip_while -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct SkipWhile { - iter: I, - flag: bool, - predicate: P, -} -impl SkipWhile { - pub(super) fn new(iter: I, predicate: P) -> SkipWhile { - SkipWhile { iter, flag: false, predicate } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for SkipWhile { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("SkipWhile").field("iter", &self.iter).field("flag", &self.flag).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for SkipWhile -where - P: FnMut(&I::Item) -> bool, -{ - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - fn check<'a, T>( - flag: &'a mut bool, - pred: &'a mut impl FnMut(&T) -> bool, - ) -> impl FnMut(&T) -> bool + 'a { - move |x| { - if *flag || !pred(x) { - *flag = true; - true - } else { - false - } - } - } - - let flag = &mut self.flag; - let pred = &mut self.predicate; - self.iter.find(check(flag, pred)) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the predicate - } - - #[inline] - fn try_fold(&mut self, mut init: Acc, mut fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - if !self.flag { - match self.next() { - Some(v) => init = fold(init, v)?, - None => return try { init }, - } - } - self.iter.try_fold(init, fold) - } - - #[inline] - fn fold(mut self, mut init: Acc, mut fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - if !self.flag { - match self.next() { - Some(v) => init = fold(init, v), - None => return init, - } - } - self.iter.fold(init, fold) - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for SkipWhile -where - I: FusedIterator, - P: FnMut(&I::Item) -> bool, -{ -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for SkipWhile -where - P: FnMut(&I::Item) -> bool, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for SkipWhile where - F: FnMut(&I::Item) -> bool -{ -} - -/// An iterator that only accepts elements while `predicate` returns `true`. -/// -/// This `struct` is created by the [`take_while`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`take_while`]: Iterator::take_while -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct TakeWhile { - iter: I, - flag: bool, - predicate: P, -} -impl TakeWhile { - pub(super) fn new(iter: I, predicate: P) -> TakeWhile { - TakeWhile { iter, flag: false, predicate } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for TakeWhile { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("TakeWhile").field("iter", &self.iter).field("flag", &self.flag).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for TakeWhile -where - P: FnMut(&I::Item) -> bool, -{ - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - if self.flag { - None - } else { - let x = self.iter.next()?; - if (self.predicate)(&x) { - Some(x) - } else { - self.flag = true; - None - } - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - if self.flag { - (0, Some(0)) - } else { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the predicate - } - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - fn check<'a, T, Acc, R: Try>( - flag: &'a mut bool, - p: &'a mut impl FnMut(&T) -> bool, - mut fold: impl FnMut(Acc, T) -> R + 'a, - ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { - move |acc, x| { - if p(&x) { - ControlFlow::from_try(fold(acc, x)) - } else { - *flag = true; - ControlFlow::Break(try { acc }) - } - } - } - - if self.flag { - try { init } - } else { - let flag = &mut self.flag; - let p = &mut self.predicate; - self.iter.try_fold(init, check(flag, p, fold)).into_try() - } - } - - #[inline] - fn fold(mut self, init: Acc, fold: Fold) -> Acc - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { - move |acc, x| Ok(f(acc, x)) - } - - self.try_fold(init, ok(fold)).unwrap() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for TakeWhile -where - I: FusedIterator, - P: FnMut(&I::Item) -> bool, -{ -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for TakeWhile -where - P: FnMut(&I::Item) -> bool, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for TakeWhile where - F: FnMut(&I::Item) -> bool -{ -} - -/// An iterator that only accepts elements while `predicate` returns `Some(_)`. -/// -/// This `struct` is created by the [`map_while`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`map_while`]: Iterator::map_while -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] -#[derive(Clone)] -pub struct MapWhile { - iter: I, - predicate: P, -} - -impl MapWhile { - pub(super) fn new(iter: I, predicate: P) -> MapWhile { - MapWhile { iter, predicate } - } -} - -#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] -impl fmt::Debug for MapWhile { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("MapWhile").field("iter", &self.iter).finish() - } -} - -#[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] -impl Iterator for MapWhile -where - P: FnMut(I::Item) -> Option, -{ - type Item = B; - - #[inline] - fn next(&mut self) -> Option { - let x = self.iter.next()?; - (self.predicate)(x) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the predicate - } - - #[inline] - fn try_fold(&mut self, init: Acc, mut fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - let Self { iter, predicate } = self; - iter.try_fold(init, |acc, x| match predicate(x) { - Some(item) => ControlFlow::from_try(fold(acc, item)), - None => ControlFlow::Break(try { acc }), - }) - .into_try() - } - - #[inline] - fn fold(mut self, init: Acc, fold: Fold) -> Acc - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { - move |acc, x| Ok(f(acc, x)) - } - - self.try_fold(init, ok(fold)).unwrap() - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for MapWhile -where - P: FnMut(I::Item) -> Option, - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for MapWhile where - P: FnMut(I::Item) -> Option -{ -} - -/// An iterator that skips over `n` elements of `iter`. -/// -/// This `struct` is created by the [`skip`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`skip`]: Iterator::skip -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Skip { - iter: I, - n: usize, -} -impl Skip { - pub(super) fn new(iter: I, n: usize) -> Skip { - Skip { iter, n } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Skip -where - I: Iterator, -{ - type Item = ::Item; - - #[inline] - fn next(&mut self) -> Option { - if self.n == 0 { - self.iter.next() - } else { - let old_n = self.n; - self.n = 0; - self.iter.nth(old_n) - } - } - - #[inline] - fn nth(&mut self, n: usize) -> Option { - // Can't just add n + self.n due to overflow. - if self.n > 0 { - let to_skip = self.n; - self.n = 0; - // nth(n) skips n+1 - self.iter.nth(to_skip - 1)?; - } - self.iter.nth(n) - } - - #[inline] - fn count(mut self) -> usize { - if self.n > 0 { - // nth(n) skips n+1 - if self.iter.nth(self.n - 1).is_none() { - return 0; - } - } - self.iter.count() - } - - #[inline] - fn last(mut self) -> Option { - if self.n > 0 { - // nth(n) skips n+1 - self.iter.nth(self.n - 1)?; - } - self.iter.last() - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (lower, upper) = self.iter.size_hint(); - - let lower = lower.saturating_sub(self.n); - let upper = match upper { - Some(x) => Some(x.saturating_sub(self.n)), - None => None, - }; - - (lower, upper) - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - let n = self.n; - self.n = 0; - if n > 0 { - // nth(n) skips n+1 - if self.iter.nth(n - 1).is_none() { - return try { init }; - } - } - self.iter.try_fold(init, fold) - } - - #[inline] - fn fold(mut self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - if self.n > 0 { - // nth(n) skips n+1 - if self.iter.nth(self.n - 1).is_none() { - return init; - } - } - self.iter.fold(init, fold) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Skip where I: ExactSizeIterator {} - -#[stable(feature = "double_ended_skip_iterator", since = "1.9.0")] -impl DoubleEndedIterator for Skip -where - I: DoubleEndedIterator + ExactSizeIterator, -{ - fn next_back(&mut self) -> Option { - if self.len() > 0 { self.iter.next_back() } else { None } - } - - #[inline] - fn nth_back(&mut self, n: usize) -> Option { - let len = self.len(); - if n < len { - self.iter.nth_back(n) - } else { - if len > 0 { - // consume the original iterator - self.iter.nth_back(len - 1); - } - None - } - } - - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - fn check>( - mut n: usize, - mut fold: impl FnMut(Acc, T) -> R, - ) -> impl FnMut(Acc, T) -> ControlFlow { - move |acc, x| { - n -= 1; - let r = fold(acc, x); - if n == 0 { ControlFlow::Break(r) } else { ControlFlow::from_try(r) } - } - } - - let n = self.len(); - if n == 0 { try { init } } else { self.iter.try_rfold(init, check(n, fold)).into_try() } - } - - fn rfold(mut self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn ok(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, T) -> Result { - move |acc, x| Ok(f(acc, x)) - } - - self.try_rfold(init, ok(fold)).unwrap() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Skip where I: FusedIterator {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Skip -where - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Skip {} - -/// An iterator that only iterates over the first `n` iterations of `iter`. -/// -/// This `struct` is created by the [`take`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`take`]: Iterator::take -/// [`Iterator`]: trait.Iterator.html -#[derive(Clone, Debug)] -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Take { - pub(super) iter: I, - pub(super) n: usize, -} -impl Take { - pub(super) fn new(iter: I, n: usize) -> Take { - Take { iter, n } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Take -where - I: Iterator, -{ - type Item = ::Item; - - #[inline] - fn next(&mut self) -> Option<::Item> { - if self.n != 0 { - self.n -= 1; - self.iter.next() - } else { - None - } - } - - #[inline] - fn nth(&mut self, n: usize) -> Option { - if self.n > n { - self.n -= n + 1; - self.iter.nth(n) - } else { - if self.n > 0 { - self.iter.nth(self.n - 1); - self.n = 0; - } - None - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - if self.n == 0 { - return (0, Some(0)); - } - - let (lower, upper) = self.iter.size_hint(); - - let lower = cmp::min(lower, self.n); - - let upper = match upper { - Some(x) if x < self.n => Some(x), - _ => Some(self.n), - }; - - (lower, upper) - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - fn check<'a, T, Acc, R: Try>( - n: &'a mut usize, - mut fold: impl FnMut(Acc, T) -> R + 'a, - ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { - move |acc, x| { - *n -= 1; - let r = fold(acc, x); - if *n == 0 { ControlFlow::Break(r) } else { ControlFlow::from_try(r) } - } - } - - if self.n == 0 { - try { init } - } else { - let n = &mut self.n; - self.iter.try_fold(init, check(n, fold)).into_try() - } - } - - #[inline] - fn fold(mut self, init: Acc, fold: Fold) -> Acc - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { - move |acc, x| Ok(f(acc, x)) - } - - self.try_fold(init, ok(fold)).unwrap() - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Take -where - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Take {} - -#[stable(feature = "double_ended_take_iterator", since = "1.38.0")] -impl DoubleEndedIterator for Take -where - I: DoubleEndedIterator + ExactSizeIterator, -{ - #[inline] - fn next_back(&mut self) -> Option { - if self.n == 0 { - None - } else { - let n = self.n; - self.n -= 1; - self.iter.nth_back(self.iter.len().saturating_sub(n)) - } - } - - #[inline] - fn nth_back(&mut self, n: usize) -> Option { - let len = self.iter.len(); - if self.n > n { - let m = len.saturating_sub(self.n) + n; - self.n -= n + 1; - self.iter.nth_back(m) - } else { - if len > 0 { - self.iter.nth_back(len - 1); - } - None - } - } - - #[inline] - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - if self.n == 0 { - try { init } - } else { - let len = self.iter.len(); - if len > self.n && self.iter.nth_back(len - self.n - 1).is_none() { - try { init } - } else { - self.iter.try_rfold(init, fold) - } - } - } - - #[inline] - fn rfold(mut self, init: Acc, fold: Fold) -> Acc - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> Acc, - { - if self.n == 0 { - init - } else { - let len = self.iter.len(); - if len > self.n && self.iter.nth_back(len - self.n - 1).is_none() { - init - } else { - self.iter.rfold(init, fold) - } - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Take where I: ExactSizeIterator {} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Take where I: FusedIterator {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Take {} - -/// An iterator to maintain state while iterating another iterator. -/// -/// This `struct` is created by the [`scan`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`scan`]: Iterator::scan -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct Scan { - iter: I, - f: F, - state: St, -} -impl Scan { - pub(super) fn new(iter: I, state: St, f: F) -> Scan { - Scan { iter, state, f } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for Scan { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Scan").field("iter", &self.iter).field("state", &self.state).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Scan -where - I: Iterator, - F: FnMut(&mut St, I::Item) -> Option, -{ - type Item = B; - - #[inline] - fn next(&mut self) -> Option { - let a = self.iter.next()?; - (self.f)(&mut self.state, a) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let (_, upper) = self.iter.size_hint(); - (0, upper) // can't know a lower bound, due to the scan function - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - fn scan<'a, T, St, B, Acc, R: Try>( - state: &'a mut St, - f: &'a mut impl FnMut(&mut St, T) -> Option, - mut fold: impl FnMut(Acc, B) -> R + 'a, - ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { - move |acc, x| match f(state, x) { - None => ControlFlow::Break(try { acc }), - Some(x) => ControlFlow::from_try(fold(acc, x)), - } - } - - let state = &mut self.state; - let f = &mut self.f; - self.iter.try_fold(init, scan(state, f, fold)).into_try() - } - - #[inline] - fn fold(mut self, init: Acc, fold: Fold) -> Acc - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> Acc, - { - #[inline] - fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { - move |acc, x| Ok(f(acc, x)) - } - - self.try_fold(init, ok(fold)).unwrap() - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Scan -where - I: SourceIter, - F: FnMut(&mut St, I::Item) -> Option, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Scan where - F: FnMut(&mut St, I::Item) -> Option -{ -} - -/// An iterator that calls a function with a reference to each element before -/// yielding it. -/// -/// This `struct` is created by the [`inspect`] method on [`Iterator`]. See its -/// documentation for more. -/// -/// [`inspect`]: Iterator::inspect -/// [`Iterator`]: trait.Iterator.html -#[must_use = "iterators are lazy and do nothing unless consumed"] -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Clone)] -pub struct Inspect { - iter: I, - f: F, -} -impl Inspect { - pub(super) fn new(iter: I, f: F) -> Inspect { - Inspect { iter, f } - } -} - -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for Inspect { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Inspect").field("iter", &self.iter).finish() - } -} - -impl Inspect -where - F: FnMut(&I::Item), -{ - #[inline] - fn do_inspect(&mut self, elt: Option) -> Option { - if let Some(ref a) = elt { - (self.f)(a); - } - - elt - } -} - -fn inspect_fold( - mut f: impl FnMut(&T), - mut fold: impl FnMut(Acc, T) -> Acc, -) -> impl FnMut(Acc, T) -> Acc { - move |acc, item| { - f(&item); - fold(acc, item) - } -} - -fn inspect_try_fold<'a, T, Acc, R>( - f: &'a mut impl FnMut(&T), - mut fold: impl FnMut(Acc, T) -> R + 'a, -) -> impl FnMut(Acc, T) -> R + 'a { - move |acc, item| { - f(&item); - fold(acc, item) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Inspect -where - F: FnMut(&I::Item), -{ - type Item = I::Item; - - #[inline] - fn next(&mut self) -> Option { - let next = self.iter.next(); - self.do_inspect(next) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - self.iter.size_hint() - } - - #[inline] - fn try_fold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_fold(init, inspect_try_fold(&mut self.f, fold)) - } - - #[inline] - fn fold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.fold(init, inspect_fold(self.f, fold)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Inspect -where - F: FnMut(&I::Item), -{ - #[inline] - fn next_back(&mut self) -> Option { - let next = self.iter.next_back(); - self.do_inspect(next) - } - - #[inline] - fn try_rfold(&mut self, init: Acc, fold: Fold) -> R - where - Self: Sized, - Fold: FnMut(Acc, Self::Item) -> R, - R: Try, - { - self.iter.try_rfold(init, inspect_try_fold(&mut self.f, fold)) - } - - #[inline] - fn rfold(self, init: Acc, fold: Fold) -> Acc - where - Fold: FnMut(Acc, Self::Item) -> Acc, - { - self.iter.rfold(init, inspect_fold(self.f, fold)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Inspect -where - F: FnMut(&I::Item), -{ - fn len(&self) -> usize { - self.iter.len() - } - - fn is_empty(&self) -> bool { - self.iter.is_empty() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Inspect where F: FnMut(&I::Item) {} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl SourceIter for Inspect -where - F: FnMut(&I::Item), - I: SourceIter, -{ - type Source = S; - - #[inline] - unsafe fn as_inner(&mut self) -> &mut S { - // SAFETY: unsafe function forwarding to unsafe function with the same requirements - unsafe { SourceIter::as_inner(&mut self.iter) } - } -} - -#[unstable(issue = "none", feature = "inplace_iteration")] -unsafe impl InPlaceIterable for Inspect where F: FnMut(&I::Item) {} - /// An iterator adapter that produces output as long as the underlying /// iterator produces `Result::Ok` values. /// diff --git a/library/core/src/iter/adapters/peekable.rs b/library/core/src/iter/adapters/peekable.rs new file mode 100644 index 0000000000000..e7fb3abc94265 --- /dev/null +++ b/library/core/src/iter/adapters/peekable.rs @@ -0,0 +1,301 @@ +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable, TrustedLen}; +use crate::ops::Try; + +/// An iterator with a `peek()` that returns an optional reference to the next +/// element. +/// +/// This `struct` is created by the [`peekable`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`peekable`]: Iterator::peekable +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Peekable { + iter: I, + /// Remember a peeked value, even if it was None. + peeked: Option>, +} + +impl Peekable { + pub(in crate::iter) fn new(iter: I) -> Peekable { + Peekable { iter, peeked: None } + } +} + +// Peekable must remember if a None has been seen in the `.peek()` method. +// It ensures that `.peek(); .peek();` or `.peek(); .next();` only advances the +// underlying iterator at most once. This does not by itself make the iterator +// fused. +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Peekable { + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + match self.peeked.take() { + Some(v) => v, + None => self.iter.next(), + } + } + + #[inline] + #[rustc_inherit_overflow_checks] + fn count(mut self) -> usize { + match self.peeked.take() { + Some(None) => 0, + Some(Some(_)) => 1 + self.iter.count(), + None => self.iter.count(), + } + } + + #[inline] + fn nth(&mut self, n: usize) -> Option { + match self.peeked.take() { + Some(None) => None, + Some(v @ Some(_)) if n == 0 => v, + Some(Some(_)) => self.iter.nth(n - 1), + None => self.iter.nth(n), + } + } + + #[inline] + fn last(mut self) -> Option { + let peek_opt = match self.peeked.take() { + Some(None) => return None, + Some(v) => v, + None => None, + }; + self.iter.last().or(peek_opt) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let peek_len = match self.peeked { + Some(None) => return (0, Some(0)), + Some(Some(_)) => 1, + None => 0, + }; + let (lo, hi) = self.iter.size_hint(); + let lo = lo.saturating_add(peek_len); + let hi = match hi { + Some(x) => x.checked_add(peek_len), + None => None, + }; + (lo, hi) + } + + #[inline] + fn try_fold(&mut self, init: B, mut f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + let acc = match self.peeked.take() { + Some(None) => return try { init }, + Some(Some(v)) => f(init, v)?, + None => init, + }; + self.iter.try_fold(acc, f) + } + + #[inline] + fn fold(self, init: Acc, mut fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + let acc = match self.peeked { + Some(None) => return init, + Some(Some(v)) => fold(init, v), + None => init, + }; + self.iter.fold(acc, fold) + } +} + +#[stable(feature = "double_ended_peek_iterator", since = "1.38.0")] +impl DoubleEndedIterator for Peekable +where + I: DoubleEndedIterator, +{ + #[inline] + fn next_back(&mut self) -> Option { + match self.peeked.as_mut() { + Some(v @ Some(_)) => self.iter.next_back().or_else(|| v.take()), + Some(None) => None, + None => self.iter.next_back(), + } + } + + #[inline] + fn try_rfold(&mut self, init: B, mut f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + match self.peeked.take() { + Some(None) => try { init }, + Some(Some(v)) => match self.iter.try_rfold(init, &mut f).into_result() { + Ok(acc) => f(acc, v), + Err(e) => { + self.peeked = Some(Some(v)); + Try::from_error(e) + } + }, + None => self.iter.try_rfold(init, f), + } + } + + #[inline] + fn rfold(self, init: Acc, mut fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + match self.peeked { + Some(None) => init, + Some(Some(v)) => { + let acc = self.iter.rfold(init, &mut fold); + fold(acc, v) + } + None => self.iter.rfold(init, fold), + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Peekable {} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Peekable {} + +impl Peekable { + /// Returns a reference to the next() value without advancing the iterator. + /// + /// Like [`next`], if there is a value, it is wrapped in a `Some(T)`. + /// But if the iteration is over, `None` is returned. + /// + /// [`next`]: Iterator::next + /// + /// Because `peek()` returns a reference, and many iterators iterate over + /// references, there can be a possibly confusing situation where the + /// return value is a double reference. You can see this effect in the + /// examples below. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// let xs = [1, 2, 3]; + /// + /// let mut iter = xs.iter().peekable(); + /// + /// // peek() lets us see into the future + /// assert_eq!(iter.peek(), Some(&&1)); + /// assert_eq!(iter.next(), Some(&1)); + /// + /// assert_eq!(iter.next(), Some(&2)); + /// + /// // The iterator does not advance even if we `peek` multiple times + /// assert_eq!(iter.peek(), Some(&&3)); + /// assert_eq!(iter.peek(), Some(&&3)); + /// + /// assert_eq!(iter.next(), Some(&3)); + /// + /// // After the iterator is finished, so is `peek()` + /// assert_eq!(iter.peek(), None); + /// assert_eq!(iter.next(), None); + /// ``` + #[inline] + #[stable(feature = "rust1", since = "1.0.0")] + pub fn peek(&mut self) -> Option<&I::Item> { + let iter = &mut self.iter; + self.peeked.get_or_insert_with(|| iter.next()).as_ref() + } + + /// Consume and return the next value of this iterator if a condition is true. + /// + /// If `func` returns `true` for the next value of this iterator, consume and return it. + /// Otherwise, return `None`. + /// + /// # Examples + /// Consume a number if it's equal to 0. + /// ``` + /// #![feature(peekable_next_if)] + /// let mut iter = (0..5).peekable(); + /// // The first item of the iterator is 0; consume it. + /// assert_eq!(iter.next_if(|&x| x == 0), Some(0)); + /// // The next item returned is now 1, so `consume` will return `false`. + /// assert_eq!(iter.next_if(|&x| x == 0), None); + /// // `next_if` saves the value of the next item if it was not equal to `expected`. + /// assert_eq!(iter.next(), Some(1)); + /// ``` + /// + /// Consume any number less than 10. + /// ``` + /// #![feature(peekable_next_if)] + /// let mut iter = (1..20).peekable(); + /// // Consume all numbers less than 10 + /// while iter.next_if(|&x| x < 10).is_some() {} + /// // The next value returned will be 10 + /// assert_eq!(iter.next(), Some(10)); + /// ``` + #[unstable(feature = "peekable_next_if", issue = "72480")] + pub fn next_if(&mut self, func: impl FnOnce(&I::Item) -> bool) -> Option { + match self.next() { + Some(matched) if func(&matched) => Some(matched), + other => { + // Since we called `self.next()`, we consumed `self.peeked`. + assert!(self.peeked.is_none()); + self.peeked = Some(other); + None + } + } + } + + /// Consume and return the next item if it is equal to `expected`. + /// + /// # Example + /// Consume a number if it's equal to 0. + /// ``` + /// #![feature(peekable_next_if)] + /// let mut iter = (0..5).peekable(); + /// // The first item of the iterator is 0; consume it. + /// assert_eq!(iter.next_if_eq(&0), Some(0)); + /// // The next item returned is now 1, so `consume` will return `false`. + /// assert_eq!(iter.next_if_eq(&0), None); + /// // `next_if_eq` saves the value of the next item if it was not equal to `expected`. + /// assert_eq!(iter.next(), Some(1)); + /// ``` + #[unstable(feature = "peekable_next_if", issue = "72480")] + pub fn next_if_eq(&mut self, expected: &T) -> Option + where + T: ?Sized, + I::Item: PartialEq, + { + self.next_if(|next| next == expected) + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Peekable where I: TrustedLen {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Peekable +where + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Peekable {} diff --git a/library/core/src/iter/adapters/rev.rs b/library/core/src/iter/adapters/rev.rs new file mode 100644 index 0000000000000..105ed40a3ed11 --- /dev/null +++ b/library/core/src/iter/adapters/rev.rs @@ -0,0 +1,137 @@ +use crate::iter::{FusedIterator, TrustedLen}; +use crate::ops::Try; + +/// A double-ended iterator with the direction inverted. +/// +/// This `struct` is created by the [`rev`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`rev`]: Iterator::rev +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Rev { + iter: T, +} + +impl Rev { + pub(in crate::iter) fn new(iter: T) -> Rev { + Rev { iter } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Rev +where + I: DoubleEndedIterator, +{ + type Item = ::Item; + + #[inline] + fn next(&mut self) -> Option<::Item> { + self.iter.next_back() + } + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + #[inline] + fn advance_by(&mut self, n: usize) -> Result<(), usize> { + self.iter.advance_back_by(n) + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<::Item> { + self.iter.nth_back(n) + } + + fn try_fold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.iter.try_rfold(init, f) + } + + fn fold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.rfold(init, f) + } + + #[inline] + fn find

(&mut self, predicate: P) -> Option + where + P: FnMut(&Self::Item) -> bool, + { + self.iter.rfind(predicate) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Rev +where + I: DoubleEndedIterator, +{ + #[inline] + fn next_back(&mut self) -> Option<::Item> { + self.iter.next() + } + + #[inline] + fn advance_back_by(&mut self, n: usize) -> Result<(), usize> { + self.iter.advance_by(n) + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<::Item> { + self.iter.nth(n) + } + + fn try_rfold(&mut self, init: B, f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + self.iter.try_fold(init, f) + } + + fn rfold(self, init: Acc, f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + self.iter.fold(init, f) + } + + fn rfind

(&mut self, predicate: P) -> Option + where + P: FnMut(&Self::Item) -> bool, + { + self.iter.find(predicate) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Rev +where + I: ExactSizeIterator + DoubleEndedIterator, +{ + fn len(&self) -> usize { + self.iter.len() + } + + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Rev where I: FusedIterator + DoubleEndedIterator {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Rev where I: TrustedLen + DoubleEndedIterator {} diff --git a/library/core/src/iter/adapters/scan.rs b/library/core/src/iter/adapters/scan.rs new file mode 100644 index 0000000000000..0214899295e35 --- /dev/null +++ b/library/core/src/iter/adapters/scan.rs @@ -0,0 +1,111 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator to maintain state while iterating another iterator. +/// +/// This `struct` is created by the [`scan`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`scan`]: Iterator::scan +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct Scan { + iter: I, + f: F, + state: St, +} + +impl Scan { + pub(in crate::iter) fn new(iter: I, state: St, f: F) -> Scan { + Scan { iter, state, f } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for Scan { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Scan").field("iter", &self.iter).field("state", &self.state).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Scan +where + I: Iterator, + F: FnMut(&mut St, I::Item) -> Option, +{ + type Item = B; + + #[inline] + fn next(&mut self) -> Option { + let a = self.iter.next()?; + (self.f)(&mut self.state, a) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the scan function + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + fn scan<'a, T, St, B, Acc, R: Try>( + state: &'a mut St, + f: &'a mut impl FnMut(&mut St, T) -> Option, + mut fold: impl FnMut(Acc, B) -> R + 'a, + ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { + move |acc, x| match f(state, x) { + None => ControlFlow::Break(try { acc }), + Some(x) => ControlFlow::from_try(fold(acc, x)), + } + } + + let state = &mut self.state; + let f = &mut self.f; + self.iter.try_fold(init, scan(state, f, fold)).into_try() + } + + #[inline] + fn fold(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { + move |acc, x| Ok(f(acc, x)) + } + + self.try_fold(init, ok(fold)).unwrap() + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Scan +where + I: SourceIter, + F: FnMut(&mut St, I::Item) -> Option, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Scan where + F: FnMut(&mut St, I::Item) -> Option +{ +} diff --git a/library/core/src/iter/adapters/skip.rs b/library/core/src/iter/adapters/skip.rs new file mode 100644 index 0000000000000..dd5325660c342 --- /dev/null +++ b/library/core/src/iter/adapters/skip.rs @@ -0,0 +1,199 @@ +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that skips over `n` elements of `iter`. +/// +/// This `struct` is created by the [`skip`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`skip`]: Iterator::skip +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Skip { + iter: I, + n: usize, +} + +impl Skip { + pub(in crate::iter) fn new(iter: I, n: usize) -> Skip { + Skip { iter, n } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Skip +where + I: Iterator, +{ + type Item = ::Item; + + #[inline] + fn next(&mut self) -> Option { + if self.n == 0 { + self.iter.next() + } else { + let old_n = self.n; + self.n = 0; + self.iter.nth(old_n) + } + } + + #[inline] + fn nth(&mut self, n: usize) -> Option { + // Can't just add n + self.n due to overflow. + if self.n > 0 { + let to_skip = self.n; + self.n = 0; + // nth(n) skips n+1 + self.iter.nth(to_skip - 1)?; + } + self.iter.nth(n) + } + + #[inline] + fn count(mut self) -> usize { + if self.n > 0 { + // nth(n) skips n+1 + if self.iter.nth(self.n - 1).is_none() { + return 0; + } + } + self.iter.count() + } + + #[inline] + fn last(mut self) -> Option { + if self.n > 0 { + // nth(n) skips n+1 + self.iter.nth(self.n - 1)?; + } + self.iter.last() + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (lower, upper) = self.iter.size_hint(); + + let lower = lower.saturating_sub(self.n); + let upper = match upper { + Some(x) => Some(x.saturating_sub(self.n)), + None => None, + }; + + (lower, upper) + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + let n = self.n; + self.n = 0; + if n > 0 { + // nth(n) skips n+1 + if self.iter.nth(n - 1).is_none() { + return try { init }; + } + } + self.iter.try_fold(init, fold) + } + + #[inline] + fn fold(mut self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + if self.n > 0 { + // nth(n) skips n+1 + if self.iter.nth(self.n - 1).is_none() { + return init; + } + } + self.iter.fold(init, fold) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Skip where I: ExactSizeIterator {} + +#[stable(feature = "double_ended_skip_iterator", since = "1.9.0")] +impl DoubleEndedIterator for Skip +where + I: DoubleEndedIterator + ExactSizeIterator, +{ + fn next_back(&mut self) -> Option { + if self.len() > 0 { self.iter.next_back() } else { None } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option { + let len = self.len(); + if n < len { + self.iter.nth_back(n) + } else { + if len > 0 { + // consume the original iterator + self.iter.nth_back(len - 1); + } + None + } + } + + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + fn check>( + mut n: usize, + mut fold: impl FnMut(Acc, T) -> R, + ) -> impl FnMut(Acc, T) -> ControlFlow { + move |acc, x| { + n -= 1; + let r = fold(acc, x); + if n == 0 { ControlFlow::Break(r) } else { ControlFlow::from_try(r) } + } + } + + let n = self.len(); + if n == 0 { try { init } } else { self.iter.try_rfold(init, check(n, fold)).into_try() } + } + + fn rfold(mut self, init: Acc, fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, T) -> Result { + move |acc, x| Ok(f(acc, x)) + } + + self.try_rfold(init, ok(fold)).unwrap() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Skip where I: FusedIterator {} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Skip +where + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Skip {} diff --git a/library/core/src/iter/adapters/skip_while.rs b/library/core/src/iter/adapters/skip_while.rs new file mode 100644 index 0000000000000..efcb469fc9577 --- /dev/null +++ b/library/core/src/iter/adapters/skip_while.rs @@ -0,0 +1,126 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::Try; + +/// An iterator that rejects elements while `predicate` returns `true`. +/// +/// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`skip_while`]: Iterator::skip_while +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct SkipWhile { + iter: I, + flag: bool, + predicate: P, +} + +impl SkipWhile { + pub(in crate::iter) fn new(iter: I, predicate: P) -> SkipWhile { + SkipWhile { iter, flag: false, predicate } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for SkipWhile { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SkipWhile").field("iter", &self.iter).field("flag", &self.flag).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for SkipWhile +where + P: FnMut(&I::Item) -> bool, +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + fn check<'a, T>( + flag: &'a mut bool, + pred: &'a mut impl FnMut(&T) -> bool, + ) -> impl FnMut(&T) -> bool + 'a { + move |x| { + if *flag || !pred(x) { + *flag = true; + true + } else { + false + } + } + } + + let flag = &mut self.flag; + let pred = &mut self.predicate; + self.iter.find(check(flag, pred)) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + + #[inline] + fn try_fold(&mut self, mut init: Acc, mut fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + if !self.flag { + match self.next() { + Some(v) => init = fold(init, v)?, + None => return try { init }, + } + } + self.iter.try_fold(init, fold) + } + + #[inline] + fn fold(mut self, mut init: Acc, mut fold: Fold) -> Acc + where + Fold: FnMut(Acc, Self::Item) -> Acc, + { + if !self.flag { + match self.next() { + Some(v) => init = fold(init, v), + None => return init, + } + } + self.iter.fold(init, fold) + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for SkipWhile +where + I: FusedIterator, + P: FnMut(&I::Item) -> bool, +{ +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for SkipWhile +where + P: FnMut(&I::Item) -> bool, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for SkipWhile where + F: FnMut(&I::Item) -> bool +{ +} diff --git a/library/core/src/iter/adapters/step_by.rs b/library/core/src/iter/adapters/step_by.rs new file mode 100644 index 0000000000000..2ba56eeccba17 --- /dev/null +++ b/library/core/src/iter/adapters/step_by.rs @@ -0,0 +1,235 @@ +use crate::{intrinsics, iter::from_fn, ops::Try}; + +/// An iterator for stepping iterators by a custom amount. +/// +/// This `struct` is created by the [`step_by`] method on [`Iterator`]. See +/// its documentation for more. +/// +/// [`step_by`]: Iterator::step_by +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "iterator_step_by", since = "1.28.0")] +#[derive(Clone, Debug)] +pub struct StepBy { + iter: I, + step: usize, + first_take: bool, +} + +impl StepBy { + pub(in crate::iter) fn new(iter: I, step: usize) -> StepBy { + assert!(step != 0); + StepBy { iter, step: step - 1, first_take: true } + } +} + +#[stable(feature = "iterator_step_by", since = "1.28.0")] +impl Iterator for StepBy +where + I: Iterator, +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + if self.first_take { + self.first_take = false; + self.iter.next() + } else { + self.iter.nth(self.step) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + #[inline] + fn first_size(step: usize) -> impl Fn(usize) -> usize { + move |n| if n == 0 { 0 } else { 1 + (n - 1) / (step + 1) } + } + + #[inline] + fn other_size(step: usize) -> impl Fn(usize) -> usize { + move |n| n / (step + 1) + } + + let (low, high) = self.iter.size_hint(); + + if self.first_take { + let f = first_size(self.step); + (f(low), high.map(f)) + } else { + let f = other_size(self.step); + (f(low), high.map(f)) + } + } + + #[inline] + fn nth(&mut self, mut n: usize) -> Option { + if self.first_take { + self.first_take = false; + let first = self.iter.next(); + if n == 0 { + return first; + } + n -= 1; + } + // n and self.step are indices, we need to add 1 to get the amount of elements + // When calling `.nth`, we need to subtract 1 again to convert back to an index + // step + 1 can't overflow because `.step_by` sets `self.step` to `step - 1` + let mut step = self.step + 1; + // n + 1 could overflow + // thus, if n is usize::MAX, instead of adding one, we call .nth(step) + if n == usize::MAX { + self.iter.nth(step - 1); + } else { + n += 1; + } + + // overflow handling + loop { + let mul = n.checked_mul(step); + { + if intrinsics::likely(mul.is_some()) { + return self.iter.nth(mul.unwrap() - 1); + } + } + let div_n = usize::MAX / n; + let div_step = usize::MAX / step; + let nth_n = div_n * n; + let nth_step = div_step * step; + let nth = if nth_n > nth_step { + step -= div_n; + nth_n + } else { + n -= div_step; + nth_step + }; + self.iter.nth(nth - 1); + } + } + + fn try_fold(&mut self, mut acc: Acc, mut f: F) -> R + where + F: FnMut(Acc, Self::Item) -> R, + R: Try, + { + #[inline] + fn nth(iter: &mut I, step: usize) -> impl FnMut() -> Option + '_ { + move || iter.nth(step) + } + + if self.first_take { + self.first_take = false; + match self.iter.next() { + None => return try { acc }, + Some(x) => acc = f(acc, x)?, + } + } + from_fn(nth(&mut self.iter, self.step)).try_fold(acc, f) + } + + fn fold(mut self, mut acc: Acc, mut f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn nth(iter: &mut I, step: usize) -> impl FnMut() -> Option + '_ { + move || iter.nth(step) + } + + if self.first_take { + self.first_take = false; + match self.iter.next() { + None => return acc, + Some(x) => acc = f(acc, x), + } + } + from_fn(nth(&mut self.iter, self.step)).fold(acc, f) + } +} + +impl StepBy +where + I: ExactSizeIterator, +{ + // The zero-based index starting from the end of the iterator of the + // last element. Used in the `DoubleEndedIterator` implementation. + fn next_back_index(&self) -> usize { + let rem = self.iter.len() % (self.step + 1); + if self.first_take { + if rem == 0 { self.step } else { rem - 1 } + } else { + rem + } + } +} + +#[stable(feature = "double_ended_step_by_iterator", since = "1.38.0")] +impl DoubleEndedIterator for StepBy +where + I: DoubleEndedIterator + ExactSizeIterator, +{ + #[inline] + fn next_back(&mut self) -> Option { + self.iter.nth_back(self.next_back_index()) + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option { + // `self.iter.nth_back(usize::MAX)` does the right thing here when `n` + // is out of bounds because the length of `self.iter` does not exceed + // `usize::MAX` (because `I: ExactSizeIterator`) and `nth_back` is + // zero-indexed + let n = n.saturating_mul(self.step + 1).saturating_add(self.next_back_index()); + self.iter.nth_back(n) + } + + fn try_rfold(&mut self, init: Acc, mut f: F) -> R + where + F: FnMut(Acc, Self::Item) -> R, + R: Try, + { + #[inline] + fn nth_back( + iter: &mut I, + step: usize, + ) -> impl FnMut() -> Option + '_ { + move || iter.nth_back(step) + } + + match self.next_back() { + None => try { init }, + Some(x) => { + let acc = f(init, x)?; + from_fn(nth_back(&mut self.iter, self.step)).try_fold(acc, f) + } + } + } + + #[inline] + fn rfold(mut self, init: Acc, mut f: F) -> Acc + where + Self: Sized, + F: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn nth_back( + iter: &mut I, + step: usize, + ) -> impl FnMut() -> Option + '_ { + move || iter.nth_back(step) + } + + match self.next_back() { + None => init, + Some(x) => { + let acc = f(init, x); + from_fn(nth_back(&mut self.iter, self.step)).fold(acc, f) + } + } + } +} + +// StepBy can only make the iterator shorter, so the len will still fit. +#[stable(feature = "iterator_step_by", since = "1.28.0")] +impl ExactSizeIterator for StepBy where I: ExactSizeIterator {} diff --git a/library/core/src/iter/adapters/take.rs b/library/core/src/iter/adapters/take.rs new file mode 100644 index 0000000000000..9efc7a480aeb4 --- /dev/null +++ b/library/core/src/iter/adapters/take.rs @@ -0,0 +1,209 @@ +use crate::cmp; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable, TrustedLen}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that only iterates over the first `n` iterations of `iter`. +/// +/// This `struct` is created by the [`take`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`take`]: Iterator::take +/// [`Iterator`]: trait.Iterator.html +#[derive(Clone, Debug)] +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Take { + iter: I, + n: usize, +} + +impl Take { + pub(in crate::iter) fn new(iter: I, n: usize) -> Take { + Take { iter, n } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Take +where + I: Iterator, +{ + type Item = ::Item; + + #[inline] + fn next(&mut self) -> Option<::Item> { + if self.n != 0 { + self.n -= 1; + self.iter.next() + } else { + None + } + } + + #[inline] + fn nth(&mut self, n: usize) -> Option { + if self.n > n { + self.n -= n + 1; + self.iter.nth(n) + } else { + if self.n > 0 { + self.iter.nth(self.n - 1); + self.n = 0; + } + None + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + if self.n == 0 { + return (0, Some(0)); + } + + let (lower, upper) = self.iter.size_hint(); + + let lower = cmp::min(lower, self.n); + + let upper = match upper { + Some(x) if x < self.n => Some(x), + _ => Some(self.n), + }; + + (lower, upper) + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + fn check<'a, T, Acc, R: Try>( + n: &'a mut usize, + mut fold: impl FnMut(Acc, T) -> R + 'a, + ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { + move |acc, x| { + *n -= 1; + let r = fold(acc, x); + if *n == 0 { ControlFlow::Break(r) } else { ControlFlow::from_try(r) } + } + } + + if self.n == 0 { + try { init } + } else { + let n = &mut self.n; + self.iter.try_fold(init, check(n, fold)).into_try() + } + } + + #[inline] + fn fold(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { + move |acc, x| Ok(f(acc, x)) + } + + self.try_fold(init, ok(fold)).unwrap() + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for Take +where + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for Take {} + +#[stable(feature = "double_ended_take_iterator", since = "1.38.0")] +impl DoubleEndedIterator for Take +where + I: DoubleEndedIterator + ExactSizeIterator, +{ + #[inline] + fn next_back(&mut self) -> Option { + if self.n == 0 { + None + } else { + let n = self.n; + self.n -= 1; + self.iter.nth_back(self.iter.len().saturating_sub(n)) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option { + let len = self.iter.len(); + if self.n > n { + let m = len.saturating_sub(self.n) + n; + self.n -= n + 1; + self.iter.nth_back(m) + } else { + if len > 0 { + self.iter.nth_back(len - 1); + } + None + } + } + + #[inline] + fn try_rfold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + if self.n == 0 { + try { init } + } else { + let len = self.iter.len(); + if len > self.n && self.iter.nth_back(len - self.n - 1).is_none() { + try { init } + } else { + self.iter.try_rfold(init, fold) + } + } + } + + #[inline] + fn rfold(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + if self.n == 0 { + init + } else { + let len = self.iter.len(); + if len > self.n && self.iter.nth_back(len - self.n - 1).is_none() { + init + } else { + self.iter.rfold(init, fold) + } + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Take where I: ExactSizeIterator {} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Take where I: FusedIterator {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Take {} diff --git a/library/core/src/iter/adapters/take_while.rs b/library/core/src/iter/adapters/take_while.rs new file mode 100644 index 0000000000000..746eb41f4c387 --- /dev/null +++ b/library/core/src/iter/adapters/take_while.rs @@ -0,0 +1,139 @@ +use crate::fmt; +use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; +use crate::ops::{ControlFlow, Try}; + +/// An iterator that only accepts elements while `predicate` returns `true`. +/// +/// This `struct` is created by the [`take_while`] method on [`Iterator`]. See its +/// documentation for more. +/// +/// [`take_while`]: Iterator::take_while +/// [`Iterator`]: trait.Iterator.html +#[must_use = "iterators are lazy and do nothing unless consumed"] +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct TakeWhile { + iter: I, + flag: bool, + predicate: P, +} + +impl TakeWhile { + pub(in crate::iter) fn new(iter: I, predicate: P) -> TakeWhile { + TakeWhile { iter, flag: false, predicate } + } +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for TakeWhile { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("TakeWhile").field("iter", &self.iter).field("flag", &self.flag).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for TakeWhile +where + P: FnMut(&I::Item) -> bool, +{ + type Item = I::Item; + + #[inline] + fn next(&mut self) -> Option { + if self.flag { + None + } else { + let x = self.iter.next()?; + if (self.predicate)(&x) { + Some(x) + } else { + self.flag = true; + None + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + if self.flag { + (0, Some(0)) + } else { + let (_, upper) = self.iter.size_hint(); + (0, upper) // can't know a lower bound, due to the predicate + } + } + + #[inline] + fn try_fold(&mut self, init: Acc, fold: Fold) -> R + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> R, + R: Try, + { + fn check<'a, T, Acc, R: Try>( + flag: &'a mut bool, + p: &'a mut impl FnMut(&T) -> bool, + mut fold: impl FnMut(Acc, T) -> R + 'a, + ) -> impl FnMut(Acc, T) -> ControlFlow + 'a { + move |acc, x| { + if p(&x) { + ControlFlow::from_try(fold(acc, x)) + } else { + *flag = true; + ControlFlow::Break(try { acc }) + } + } + } + + if self.flag { + try { init } + } else { + let flag = &mut self.flag; + let p = &mut self.predicate; + self.iter.try_fold(init, check(flag, p, fold)).into_try() + } + } + + #[inline] + fn fold(mut self, init: Acc, fold: Fold) -> Acc + where + Self: Sized, + Fold: FnMut(Acc, Self::Item) -> Acc, + { + #[inline] + fn ok(mut f: impl FnMut(B, T) -> B) -> impl FnMut(B, T) -> Result { + move |acc, x| Ok(f(acc, x)) + } + + self.try_fold(init, ok(fold)).unwrap() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for TakeWhile +where + I: FusedIterator, + P: FnMut(&I::Item) -> bool, +{ +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl SourceIter for TakeWhile +where + P: FnMut(&I::Item) -> bool, + I: SourceIter, +{ + type Source = S; + + #[inline] + unsafe fn as_inner(&mut self) -> &mut S { + // SAFETY: unsafe function forwarding to unsafe function with the same requirements + unsafe { SourceIter::as_inner(&mut self.iter) } + } +} + +#[unstable(issue = "none", feature = "inplace_iteration")] +unsafe impl InPlaceIterable for TakeWhile where + F: FnMut(&I::Item) -> bool +{ +} diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs index 78712988eaea7..8cd4c77523192 100644 --- a/library/core/src/iter/adapters/zip.rs +++ b/library/core/src/iter/adapters/zip.rs @@ -1,10 +1,7 @@ use crate::cmp; use crate::fmt::{self, Debug}; - -use super::super::{ - DoubleEndedIterator, ExactSizeIterator, FusedIterator, InPlaceIterable, Iterator, SourceIter, - TrustedLen, -}; +use crate::iter::{DoubleEndedIterator, ExactSizeIterator, FusedIterator, Iterator}; +use crate::iter::{InPlaceIterable, SourceIter, TrustedLen}; /// An iterator that iterates two other iterators simultaneously. /// @@ -21,7 +18,7 @@ pub struct Zip { len: usize, } impl Zip { - pub(in super::super) fn new(a: A, b: B) -> Zip { + pub(in crate::iter) fn new(a: A, b: B) -> Zip { ZipImpl::new(a, b) } fn super_nth(&mut self, mut n: usize) -> Option<(A::Item, B::Item)> { diff --git a/library/core/src/iter/mod.rs b/library/core/src/iter/mod.rs index 59f333e888b88..072373c00f679 100644 --- a/library/core/src/iter/mod.rs +++ b/library/core/src/iter/mod.rs @@ -335,15 +335,14 @@ pub use self::sources::{successors, Successors}; #[stable(feature = "fused", since = "1.26.0")] pub use self::traits::FusedIterator; +#[unstable(issue = "none", feature = "inplace_iteration")] +pub use self::traits::InPlaceIterable; #[unstable(feature = "trusted_len", issue = "37572")] pub use self::traits::TrustedLen; #[stable(feature = "rust1", since = "1.0.0")] -pub use self::traits::{DoubleEndedIterator, Extend, FromIterator, IntoIterator}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::traits::{ExactSizeIterator, Product, Sum}; - -#[unstable(issue = "none", feature = "inplace_iteration")] -pub use self::traits::InPlaceIterable; +pub use self::traits::{ + DoubleEndedIterator, ExactSizeIterator, Extend, FromIterator, IntoIterator, Product, Sum, +}; #[stable(feature = "iter_cloned", since = "1.1.0")] pub use self::adapters::Cloned; @@ -351,21 +350,19 @@ pub use self::adapters::Cloned; pub use self::adapters::Copied; #[stable(feature = "iterator_flatten", since = "1.29.0")] pub use self::adapters::Flatten; - #[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")] pub use self::adapters::MapWhile; -#[unstable(issue = "none", feature = "inplace_iteration")] +#[unstable(feature = "inplace_iteration", issue = "none")] pub use self::adapters::SourceIter; #[stable(feature = "iterator_step_by", since = "1.28.0")] pub use self::adapters::StepBy; #[unstable(feature = "trusted_random_access", issue = "none")] pub use self::adapters::TrustedRandomAccess; #[stable(feature = "rust1", since = "1.0.0")] -pub use self::adapters::{Chain, Cycle, Enumerate, Filter, FilterMap, Map, Rev, Zip}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::adapters::{FlatMap, Peekable, Scan, Skip, SkipWhile, Take, TakeWhile}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::adapters::{Fuse, Inspect}; +pub use self::adapters::{ + Chain, Cycle, Enumerate, Filter, FilterMap, FlatMap, Fuse, Inspect, Map, Peekable, Rev, Scan, + Skip, SkipWhile, Take, TakeWhile, Zip, +}; pub(crate) use self::adapters::process_results; diff --git a/library/core/src/iter/sources.rs b/library/core/src/iter/sources.rs index 44da8f4715c88..de0663141e252 100644 --- a/library/core/src/iter/sources.rs +++ b/library/core/src/iter/sources.rs @@ -1,625 +1,27 @@ -use crate::fmt; -use crate::marker; +mod empty; +mod from_fn; +mod once; +mod once_with; +mod repeat; +mod repeat_with; +mod successors; -use super::{FusedIterator, TrustedLen}; +pub use self::repeat::{repeat, Repeat}; -/// An iterator that repeats an element endlessly. -/// -/// This `struct` is created by the [`repeat()`] function. See its documentation for more. -#[derive(Clone, Debug)] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Repeat { - element: A, -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for Repeat { - type Item = A; - - #[inline] - fn next(&mut self) -> Option { - Some(self.element.clone()) - } - #[inline] - fn size_hint(&self) -> (usize, Option) { - (usize::MAX, None) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for Repeat { - #[inline] - fn next_back(&mut self) -> Option { - Some(self.element.clone()) - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Repeat {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Repeat {} - -/// Creates a new iterator that endlessly repeats a single element. -/// -/// The `repeat()` function repeats a single value over and over again. -/// -/// Infinite iterators like `repeat()` are often used with adapters like -/// [`Iterator::take()`], in order to make them finite. -/// -/// If the element type of the iterator you need does not implement `Clone`, -/// or if you do not want to keep the repeated element in memory, you can -/// instead use the [`repeat_with()`] function. -/// -/// # Examples -/// -/// Basic usage: -/// -/// ``` -/// use std::iter; -/// -/// // the number four 4ever: -/// let mut fours = iter::repeat(4); -/// -/// assert_eq!(Some(4), fours.next()); -/// assert_eq!(Some(4), fours.next()); -/// assert_eq!(Some(4), fours.next()); -/// assert_eq!(Some(4), fours.next()); -/// assert_eq!(Some(4), fours.next()); -/// -/// // yup, still four -/// assert_eq!(Some(4), fours.next()); -/// ``` -/// -/// Going finite with [`Iterator::take()`]: -/// -/// ``` -/// use std::iter; -/// -/// // that last example was too many fours. Let's only have four fours. -/// let mut four_fours = iter::repeat(4).take(4); -/// -/// assert_eq!(Some(4), four_fours.next()); -/// assert_eq!(Some(4), four_fours.next()); -/// assert_eq!(Some(4), four_fours.next()); -/// assert_eq!(Some(4), four_fours.next()); -/// -/// // ... and now we're done -/// assert_eq!(None, four_fours.next()); -/// ``` -#[inline] -#[stable(feature = "rust1", since = "1.0.0")] -pub fn repeat(elt: T) -> Repeat { - Repeat { element: elt } -} - -/// An iterator that repeats elements of type `A` endlessly by -/// applying the provided closure `F: FnMut() -> A`. -/// -/// This `struct` is created by the [`repeat_with()`] function. -/// See its documentation for more. -#[derive(Copy, Clone, Debug)] -#[stable(feature = "iterator_repeat_with", since = "1.28.0")] -pub struct RepeatWith { - repeater: F, -} - -#[stable(feature = "iterator_repeat_with", since = "1.28.0")] -impl A> Iterator for RepeatWith { - type Item = A; - - #[inline] - fn next(&mut self) -> Option { - Some((self.repeater)()) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - (usize::MAX, None) - } -} - -#[stable(feature = "iterator_repeat_with", since = "1.28.0")] -impl A> FusedIterator for RepeatWith {} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl A> TrustedLen for RepeatWith {} - -/// Creates a new iterator that repeats elements of type `A` endlessly by -/// applying the provided closure, the repeater, `F: FnMut() -> A`. -/// -/// The `repeat_with()` function calls the repeater over and over again. -/// -/// Infinite iterators like `repeat_with()` are often used with adapters like -/// [`Iterator::take()`], in order to make them finite. -/// -/// If the element type of the iterator you need implements [`Clone`], and -/// it is OK to keep the source element in memory, you should instead use -/// the [`repeat()`] function. -/// -/// An iterator produced by `repeat_with()` is not a [`DoubleEndedIterator`]. -/// If you need `repeat_with()` to return a [`DoubleEndedIterator`], -/// please open a GitHub issue explaining your use case. -/// -/// [`DoubleEndedIterator`]: crate::iter::DoubleEndedIterator -/// -/// # Examples -/// -/// Basic usage: -/// -/// ``` -/// use std::iter; -/// -/// // let's assume we have some value of a type that is not `Clone` -/// // or which don't want to have in memory just yet because it is expensive: -/// #[derive(PartialEq, Debug)] -/// struct Expensive; -/// -/// // a particular value forever: -/// let mut things = iter::repeat_with(|| Expensive); -/// -/// assert_eq!(Some(Expensive), things.next()); -/// assert_eq!(Some(Expensive), things.next()); -/// assert_eq!(Some(Expensive), things.next()); -/// assert_eq!(Some(Expensive), things.next()); -/// assert_eq!(Some(Expensive), things.next()); -/// ``` -/// -/// Using mutation and going finite: -/// -/// ```rust -/// use std::iter; -/// -/// // From the zeroth to the third power of two: -/// let mut curr = 1; -/// let mut pow2 = iter::repeat_with(|| { let tmp = curr; curr *= 2; tmp }) -/// .take(4); -/// -/// assert_eq!(Some(1), pow2.next()); -/// assert_eq!(Some(2), pow2.next()); -/// assert_eq!(Some(4), pow2.next()); -/// assert_eq!(Some(8), pow2.next()); -/// -/// // ... and now we're done -/// assert_eq!(None, pow2.next()); -/// ``` -#[inline] -#[stable(feature = "iterator_repeat_with", since = "1.28.0")] -pub fn repeat_with A>(repeater: F) -> RepeatWith { - RepeatWith { repeater } -} - -/// An iterator that yields nothing. -/// -/// This `struct` is created by the [`empty()`] function. See its documentation for more. #[stable(feature = "iter_empty", since = "1.2.0")] -pub struct Empty(marker::PhantomData); - -#[stable(feature = "iter_empty_send_sync", since = "1.42.0")] -unsafe impl Send for Empty {} -#[stable(feature = "iter_empty_send_sync", since = "1.42.0")] -unsafe impl Sync for Empty {} +pub use self::empty::{empty, Empty}; -#[stable(feature = "core_impl_debug", since = "1.9.0")] -impl fmt::Debug for Empty { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.pad("Empty") - } -} - -#[stable(feature = "iter_empty", since = "1.2.0")] -impl Iterator for Empty { - type Item = T; - - fn next(&mut self) -> Option { - None - } - - fn size_hint(&self) -> (usize, Option) { - (0, Some(0)) - } -} - -#[stable(feature = "iter_empty", since = "1.2.0")] -impl DoubleEndedIterator for Empty { - fn next_back(&mut self) -> Option { - None - } -} - -#[stable(feature = "iter_empty", since = "1.2.0")] -impl ExactSizeIterator for Empty { - fn len(&self) -> usize { - 0 - } -} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Empty {} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Empty {} - -// not #[derive] because that adds a Clone bound on T, -// which isn't necessary. -#[stable(feature = "iter_empty", since = "1.2.0")] -impl Clone for Empty { - fn clone(&self) -> Empty { - Empty(marker::PhantomData) - } -} - -// not #[derive] because that adds a Default bound on T, -// which isn't necessary. -#[stable(feature = "iter_empty", since = "1.2.0")] -impl Default for Empty { - fn default() -> Empty { - Empty(marker::PhantomData) - } -} - -/// Creates an iterator that yields nothing. -/// -/// # Examples -/// -/// Basic usage: -/// -/// ``` -/// use std::iter; -/// -/// // this could have been an iterator over i32, but alas, it's just not. -/// let mut nope = iter::empty::(); -/// -/// assert_eq!(None, nope.next()); -/// ``` -#[stable(feature = "iter_empty", since = "1.2.0")] -#[rustc_const_stable(feature = "const_iter_empty", since = "1.32.0")] -pub const fn empty() -> Empty { - Empty(marker::PhantomData) -} - -/// An iterator that yields an element exactly once. -/// -/// This `struct` is created by the [`once()`] function. See its documentation for more. -#[derive(Clone, Debug)] #[stable(feature = "iter_once", since = "1.2.0")] -pub struct Once { - inner: crate::option::IntoIter, -} +pub use self::once::{once, Once}; -#[stable(feature = "iter_once", since = "1.2.0")] -impl Iterator for Once { - type Item = T; - - fn next(&mut self) -> Option { - self.inner.next() - } - - fn size_hint(&self) -> (usize, Option) { - self.inner.size_hint() - } -} - -#[stable(feature = "iter_once", since = "1.2.0")] -impl DoubleEndedIterator for Once { - fn next_back(&mut self) -> Option { - self.inner.next_back() - } -} - -#[stable(feature = "iter_once", since = "1.2.0")] -impl ExactSizeIterator for Once { - fn len(&self) -> usize { - self.inner.len() - } -} - -#[unstable(feature = "trusted_len", issue = "37572")] -unsafe impl TrustedLen for Once {} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Once {} - -/// Creates an iterator that yields an element exactly once. -/// -/// This is commonly used to adapt a single value into a [`chain()`] of other -/// kinds of iteration. Maybe you have an iterator that covers almost -/// everything, but you need an extra special case. Maybe you have a function -/// which works on iterators, but you only need to process one value. -/// -/// [`chain()`]: Iterator::chain -/// -/// # Examples -/// -/// Basic usage: -/// -/// ``` -/// use std::iter; -/// -/// // one is the loneliest number -/// let mut one = iter::once(1); -/// -/// assert_eq!(Some(1), one.next()); -/// -/// // just one, that's all we get -/// assert_eq!(None, one.next()); -/// ``` -/// -/// Chaining together with another iterator. Let's say that we want to iterate -/// over each file of the `.foo` directory, but also a configuration file, -/// `.foorc`: -/// -/// ```no_run -/// use std::iter; -/// use std::fs; -/// use std::path::PathBuf; -/// -/// let dirs = fs::read_dir(".foo").unwrap(); -/// -/// // we need to convert from an iterator of DirEntry-s to an iterator of -/// // PathBufs, so we use map -/// let dirs = dirs.map(|file| file.unwrap().path()); -/// -/// // now, our iterator just for our config file -/// let config = iter::once(PathBuf::from(".foorc")); -/// -/// // chain the two iterators together into one big iterator -/// let files = dirs.chain(config); -/// -/// // this will give us all of the files in .foo as well as .foorc -/// for f in files { -/// println!("{:?}", f); -/// } -/// ``` -#[stable(feature = "iter_once", since = "1.2.0")] -pub fn once(value: T) -> Once { - Once { inner: Some(value).into_iter() } -} - -/// An iterator that yields a single element of type `A` by -/// applying the provided closure `F: FnOnce() -> A`. -/// -/// This `struct` is created by the [`once_with()`] function. -/// See its documentation for more. -#[derive(Clone, Debug)] -#[stable(feature = "iter_once_with", since = "1.43.0")] -pub struct OnceWith { - gen: Option, -} - -#[stable(feature = "iter_once_with", since = "1.43.0")] -impl A> Iterator for OnceWith { - type Item = A; - - #[inline] - fn next(&mut self) -> Option { - let f = self.gen.take()?; - Some(f()) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - self.gen.iter().size_hint() - } -} - -#[stable(feature = "iter_once_with", since = "1.43.0")] -impl A> DoubleEndedIterator for OnceWith { - fn next_back(&mut self) -> Option { - self.next() - } -} - -#[stable(feature = "iter_once_with", since = "1.43.0")] -impl A> ExactSizeIterator for OnceWith { - fn len(&self) -> usize { - self.gen.iter().len() - } -} - -#[stable(feature = "iter_once_with", since = "1.43.0")] -impl A> FusedIterator for OnceWith {} - -#[stable(feature = "iter_once_with", since = "1.43.0")] -unsafe impl A> TrustedLen for OnceWith {} - -/// Creates an iterator that lazily generates a value exactly once by invoking -/// the provided closure. -/// -/// This is commonly used to adapt a single value generator into a [`chain()`] of -/// other kinds of iteration. Maybe you have an iterator that covers almost -/// everything, but you need an extra special case. Maybe you have a function -/// which works on iterators, but you only need to process one value. -/// -/// Unlike [`once()`], this function will lazily generate the value on request. -/// -/// [`chain()`]: Iterator::chain -/// -/// # Examples -/// -/// Basic usage: -/// -/// ``` -/// use std::iter; -/// -/// // one is the loneliest number -/// let mut one = iter::once_with(|| 1); -/// -/// assert_eq!(Some(1), one.next()); -/// -/// // just one, that's all we get -/// assert_eq!(None, one.next()); -/// ``` -/// -/// Chaining together with another iterator. Let's say that we want to iterate -/// over each file of the `.foo` directory, but also a configuration file, -/// `.foorc`: -/// -/// ```no_run -/// use std::iter; -/// use std::fs; -/// use std::path::PathBuf; -/// -/// let dirs = fs::read_dir(".foo").unwrap(); -/// -/// // we need to convert from an iterator of DirEntry-s to an iterator of -/// // PathBufs, so we use map -/// let dirs = dirs.map(|file| file.unwrap().path()); -/// -/// // now, our iterator just for our config file -/// let config = iter::once_with(|| PathBuf::from(".foorc")); -/// -/// // chain the two iterators together into one big iterator -/// let files = dirs.chain(config); -/// -/// // this will give us all of the files in .foo as well as .foorc -/// for f in files { -/// println!("{:?}", f); -/// } -/// ``` -#[inline] -#[stable(feature = "iter_once_with", since = "1.43.0")] -pub fn once_with A>(gen: F) -> OnceWith { - OnceWith { gen: Some(gen) } -} - -/// Creates a new iterator where each iteration calls the provided closure -/// `F: FnMut() -> Option`. -/// -/// This allows creating a custom iterator with any behavior -/// without using the more verbose syntax of creating a dedicated type -/// and implementing the [`Iterator`] trait for it. -/// -/// Note that the `FromFn` iterator doesn’t make assumptions about the behavior of the closure, -/// and therefore conservatively does not implement [`FusedIterator`], -/// or override [`Iterator::size_hint()`] from its default `(0, None)`. -/// -/// The closure can use captures and its environment to track state across iterations. Depending on -/// how the iterator is used, this may require specifying the [`move`] keyword on the closure. -/// -/// [`move`]: ../../std/keyword.move.html -/// -/// # Examples -/// -/// Let’s re-implement the counter iterator from the [module-level documentation]: -/// -/// [module-level documentation]: super -/// -/// ``` -/// let mut count = 0; -/// let counter = std::iter::from_fn(move || { -/// // Increment our count. This is why we started at zero. -/// count += 1; -/// -/// // Check to see if we've finished counting or not. -/// if count < 6 { -/// Some(count) -/// } else { -/// None -/// } -/// }); -/// assert_eq!(counter.collect::>(), &[1, 2, 3, 4, 5]); -/// ``` -#[inline] -#[stable(feature = "iter_from_fn", since = "1.34.0")] -pub fn from_fn(f: F) -> FromFn -where - F: FnMut() -> Option, -{ - FromFn(f) -} - -/// An iterator where each iteration calls the provided closure `F: FnMut() -> Option`. -/// -/// This `struct` is created by the [`iter::from_fn()`] function. -/// See its documentation for more. -/// -/// [`iter::from_fn()`]: from_fn -#[derive(Clone)] -#[stable(feature = "iter_from_fn", since = "1.34.0")] -pub struct FromFn(F); - -#[stable(feature = "iter_from_fn", since = "1.34.0")] -impl Iterator for FromFn -where - F: FnMut() -> Option, -{ - type Item = T; - - #[inline] - fn next(&mut self) -> Option { - (self.0)() - } -} +#[stable(feature = "iterator_repeat_with", since = "1.28.0")] +pub use self::repeat_with::{repeat_with, RepeatWith}; #[stable(feature = "iter_from_fn", since = "1.34.0")] -impl fmt::Debug for FromFn { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("FromFn").finish() - } -} +pub use self::from_fn::{from_fn, FromFn}; -/// Creates a new iterator where each successive item is computed based on the preceding one. -/// -/// The iterator starts with the given first item (if any) -/// and calls the given `FnMut(&T) -> Option` closure to compute each item’s successor. -/// -/// ``` -/// use std::iter::successors; -/// -/// let powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10)); -/// assert_eq!(powers_of_10.collect::>(), &[1, 10, 100, 1_000, 10_000]); -/// ``` #[stable(feature = "iter_successors", since = "1.34.0")] -pub fn successors(first: Option, succ: F) -> Successors -where - F: FnMut(&T) -> Option, -{ - // If this function returned `impl Iterator` - // it could be based on `unfold` and not need a dedicated type. - // However having a named `Successors` type allows it to be `Clone` when `T` and `F` are. - Successors { next: first, succ } -} +pub use self::successors::{successors, Successors}; -/// An new iterator where each successive item is computed based on the preceding one. -/// -/// This `struct` is created by the [`iter::successors()`] function. -/// See its documentation for more. -/// -/// [`iter::successors()`]: successors -#[derive(Clone)] -#[stable(feature = "iter_successors", since = "1.34.0")] -pub struct Successors { - next: Option, - succ: F, -} - -#[stable(feature = "iter_successors", since = "1.34.0")] -impl Iterator for Successors -where - F: FnMut(&T) -> Option, -{ - type Item = T; - - #[inline] - fn next(&mut self) -> Option { - let item = self.next.take()?; - self.next = (self.succ)(&item); - Some(item) - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - if self.next.is_some() { (1, None) } else { (0, Some(0)) } - } -} - -#[stable(feature = "iter_successors", since = "1.34.0")] -impl FusedIterator for Successors where F: FnMut(&T) -> Option {} - -#[stable(feature = "iter_successors", since = "1.34.0")] -impl fmt::Debug for Successors { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Successors").field("next", &self.next).finish() - } -} +#[stable(feature = "iter_once_with", since = "1.43.0")] +pub use self::once_with::{once_with, OnceWith}; diff --git a/library/core/src/iter/sources/empty.rs b/library/core/src/iter/sources/empty.rs new file mode 100644 index 0000000000000..5d4a9fe8c6cc0 --- /dev/null +++ b/library/core/src/iter/sources/empty.rs @@ -0,0 +1,92 @@ +use crate::fmt; +use crate::iter::{FusedIterator, TrustedLen}; +use crate::marker; + +/// Creates an iterator that yields nothing. +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// use std::iter; +/// +/// // this could have been an iterator over i32, but alas, it's just not. +/// let mut nope = iter::empty::(); +/// +/// assert_eq!(None, nope.next()); +/// ``` +#[stable(feature = "iter_empty", since = "1.2.0")] +#[rustc_const_stable(feature = "const_iter_empty", since = "1.32.0")] +pub const fn empty() -> Empty { + Empty(marker::PhantomData) +} + +/// An iterator that yields nothing. +/// +/// This `struct` is created by the [`empty()`] function. See its documentation for more. +#[stable(feature = "iter_empty", since = "1.2.0")] +pub struct Empty(marker::PhantomData); + +#[stable(feature = "iter_empty_send_sync", since = "1.42.0")] +unsafe impl Send for Empty {} +#[stable(feature = "iter_empty_send_sync", since = "1.42.0")] +unsafe impl Sync for Empty {} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl fmt::Debug for Empty { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.pad("Empty") + } +} + +#[stable(feature = "iter_empty", since = "1.2.0")] +impl Iterator for Empty { + type Item = T; + + fn next(&mut self) -> Option { + None + } + + fn size_hint(&self) -> (usize, Option) { + (0, Some(0)) + } +} + +#[stable(feature = "iter_empty", since = "1.2.0")] +impl DoubleEndedIterator for Empty { + fn next_back(&mut self) -> Option { + None + } +} + +#[stable(feature = "iter_empty", since = "1.2.0")] +impl ExactSizeIterator for Empty { + fn len(&self) -> usize { + 0 + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Empty {} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Empty {} + +// not #[derive] because that adds a Clone bound on T, +// which isn't necessary. +#[stable(feature = "iter_empty", since = "1.2.0")] +impl Clone for Empty { + fn clone(&self) -> Empty { + Empty(marker::PhantomData) + } +} + +// not #[derive] because that adds a Default bound on T, +// which isn't necessary. +#[stable(feature = "iter_empty", since = "1.2.0")] +impl Default for Empty { + fn default() -> Empty { + Empty(marker::PhantomData) + } +} diff --git a/library/core/src/iter/sources/from_fn.rs b/library/core/src/iter/sources/from_fn.rs new file mode 100644 index 0000000000000..3cd3830471cfe --- /dev/null +++ b/library/core/src/iter/sources/from_fn.rs @@ -0,0 +1,78 @@ +use crate::fmt; + +/// Creates a new iterator where each iteration calls the provided closure +/// `F: FnMut() -> Option`. +/// +/// This allows creating a custom iterator with any behavior +/// without using the more verbose syntax of creating a dedicated type +/// and implementing the [`Iterator`] trait for it. +/// +/// Note that the `FromFn` iterator doesn’t make assumptions about the behavior of the closure, +/// and therefore conservatively does not implement [`FusedIterator`], +/// or override [`Iterator::size_hint()`] from its default `(0, None)`. +/// +/// The closure can use captures and its environment to track state across iterations. Depending on +/// how the iterator is used, this may require specifying the [`move`] keyword on the closure. +/// +/// [`move`]: ../../std/keyword.move.html +/// [`FusedIterator`]: crate::iter::FusedIterator +/// +/// # Examples +/// +/// Let’s re-implement the counter iterator from [module-level documentation]: +/// +/// [module-level documentation]: crate::iter +/// +/// ``` +/// let mut count = 0; +/// let counter = std::iter::from_fn(move || { +/// // Increment our count. This is why we started at zero. +/// count += 1; +/// +/// // Check to see if we've finished counting or not. +/// if count < 6 { +/// Some(count) +/// } else { +/// None +/// } +/// }); +/// assert_eq!(counter.collect::>(), &[1, 2, 3, 4, 5]); +/// ``` +#[inline] +#[stable(feature = "iter_from_fn", since = "1.34.0")] +pub fn from_fn(f: F) -> FromFn +where + F: FnMut() -> Option, +{ + FromFn(f) +} + +/// An iterator where each iteration calls the provided closure `F: FnMut() -> Option`. +/// +/// This `struct` is created by the [`iter::from_fn()`] function. +/// See its documentation for more. +/// +/// [`iter::from_fn()`]: from_fn +#[derive(Clone)] +#[stable(feature = "iter_from_fn", since = "1.34.0")] +pub struct FromFn(F); + +#[stable(feature = "iter_from_fn", since = "1.34.0")] +impl Iterator for FromFn +where + F: FnMut() -> Option, +{ + type Item = T; + + #[inline] + fn next(&mut self) -> Option { + (self.0)() + } +} + +#[stable(feature = "iter_from_fn", since = "1.34.0")] +impl fmt::Debug for FromFn { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("FromFn").finish() + } +} diff --git a/library/core/src/iter/sources/once.rs b/library/core/src/iter/sources/once.rs new file mode 100644 index 0000000000000..27bc3dcfd79e0 --- /dev/null +++ b/library/core/src/iter/sources/once.rs @@ -0,0 +1,99 @@ +use crate::iter::{FusedIterator, TrustedLen}; + +/// Creates an iterator that yields an element exactly once. +/// +/// This is commonly used to adapt a single value into a [`chain()`] of other +/// kinds of iteration. Maybe you have an iterator that covers almost +/// everything, but you need an extra special case. Maybe you have a function +/// which works on iterators, but you only need to process one value. +/// +/// [`chain()`]: Iterator::chain +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// use std::iter; +/// +/// // one is the loneliest number +/// let mut one = iter::once(1); +/// +/// assert_eq!(Some(1), one.next()); +/// +/// // just one, that's all we get +/// assert_eq!(None, one.next()); +/// ``` +/// +/// Chaining together with another iterator. Let's say that we want to iterate +/// over each file of the `.foo` directory, but also a configuration file, +/// `.foorc`: +/// +/// ```no_run +/// use std::iter; +/// use std::fs; +/// use std::path::PathBuf; +/// +/// let dirs = fs::read_dir(".foo").unwrap(); +/// +/// // we need to convert from an iterator of DirEntry-s to an iterator of +/// // PathBufs, so we use map +/// let dirs = dirs.map(|file| file.unwrap().path()); +/// +/// // now, our iterator just for our config file +/// let config = iter::once(PathBuf::from(".foorc")); +/// +/// // chain the two iterators together into one big iterator +/// let files = dirs.chain(config); +/// +/// // this will give us all of the files in .foo as well as .foorc +/// for f in files { +/// println!("{:?}", f); +/// } +/// ``` +#[stable(feature = "iter_once", since = "1.2.0")] +pub fn once(value: T) -> Once { + Once { inner: Some(value).into_iter() } +} + +/// An iterator that yields an element exactly once. +/// +/// This `struct` is created by the [`once()`] function. See its documentation for more. +#[derive(Clone, Debug)] +#[stable(feature = "iter_once", since = "1.2.0")] +pub struct Once { + inner: crate::option::IntoIter, +} + +#[stable(feature = "iter_once", since = "1.2.0")] +impl Iterator for Once { + type Item = T; + + fn next(&mut self) -> Option { + self.inner.next() + } + + fn size_hint(&self) -> (usize, Option) { + self.inner.size_hint() + } +} + +#[stable(feature = "iter_once", since = "1.2.0")] +impl DoubleEndedIterator for Once { + fn next_back(&mut self) -> Option { + self.inner.next_back() + } +} + +#[stable(feature = "iter_once", since = "1.2.0")] +impl ExactSizeIterator for Once { + fn len(&self) -> usize { + self.inner.len() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Once {} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Once {} diff --git a/library/core/src/iter/sources/once_with.rs b/library/core/src/iter/sources/once_with.rs new file mode 100644 index 0000000000000..cf6a3c1152452 --- /dev/null +++ b/library/core/src/iter/sources/once_with.rs @@ -0,0 +1,109 @@ +use crate::iter::{FusedIterator, TrustedLen}; + +/// Creates an iterator that lazily generates a value exactly once by invoking +/// the provided closure. +/// +/// This is commonly used to adapt a single value generator into a [`chain()`] of +/// other kinds of iteration. Maybe you have an iterator that covers almost +/// everything, but you need an extra special case. Maybe you have a function +/// which works on iterators, but you only need to process one value. +/// +/// Unlike [`once()`], this function will lazily generate the value on request. +/// +/// [`chain()`]: Iterator::chain +/// [`once()`]: crate::iter::once +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// use std::iter; +/// +/// // one is the loneliest number +/// let mut one = iter::once_with(|| 1); +/// +/// assert_eq!(Some(1), one.next()); +/// +/// // just one, that's all we get +/// assert_eq!(None, one.next()); +/// ``` +/// +/// Chaining together with another iterator. Let's say that we want to iterate +/// over each file of the `.foo` directory, but also a configuration file, +/// `.foorc`: +/// +/// ```no_run +/// use std::iter; +/// use std::fs; +/// use std::path::PathBuf; +/// +/// let dirs = fs::read_dir(".foo").unwrap(); +/// +/// // we need to convert from an iterator of DirEntry-s to an iterator of +/// // PathBufs, so we use map +/// let dirs = dirs.map(|file| file.unwrap().path()); +/// +/// // now, our iterator just for our config file +/// let config = iter::once_with(|| PathBuf::from(".foorc")); +/// +/// // chain the two iterators together into one big iterator +/// let files = dirs.chain(config); +/// +/// // this will give us all of the files in .foo as well as .foorc +/// for f in files { +/// println!("{:?}", f); +/// } +/// ``` +#[inline] +#[stable(feature = "iter_once_with", since = "1.43.0")] +pub fn once_with A>(gen: F) -> OnceWith { + OnceWith { gen: Some(gen) } +} + +/// An iterator that yields a single element of type `A` by +/// applying the provided closure `F: FnOnce() -> A`. +/// +/// This `struct` is created by the [`once_with()`] function. +/// See its documentation for more. +#[derive(Clone, Debug)] +#[stable(feature = "iter_once_with", since = "1.43.0")] +pub struct OnceWith { + gen: Option, +} + +#[stable(feature = "iter_once_with", since = "1.43.0")] +impl A> Iterator for OnceWith { + type Item = A; + + #[inline] + fn next(&mut self) -> Option { + let f = self.gen.take()?; + Some(f()) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.gen.iter().size_hint() + } +} + +#[stable(feature = "iter_once_with", since = "1.43.0")] +impl A> DoubleEndedIterator for OnceWith { + fn next_back(&mut self) -> Option { + self.next() + } +} + +#[stable(feature = "iter_once_with", since = "1.43.0")] +impl A> ExactSizeIterator for OnceWith { + fn len(&self) -> usize { + self.gen.iter().len() + } +} + +#[stable(feature = "iter_once_with", since = "1.43.0")] +impl A> FusedIterator for OnceWith {} + +#[stable(feature = "iter_once_with", since = "1.43.0")] +unsafe impl A> TrustedLen for OnceWith {} diff --git a/library/core/src/iter/sources/repeat.rs b/library/core/src/iter/sources/repeat.rs new file mode 100644 index 0000000000000..d1f2879235f1a --- /dev/null +++ b/library/core/src/iter/sources/repeat.rs @@ -0,0 +1,93 @@ +use crate::iter::{FusedIterator, TrustedLen}; + +/// Creates a new iterator that endlessly repeats a single element. +/// +/// The `repeat()` function repeats a single value over and over again. +/// +/// Infinite iterators like `repeat()` are often used with adapters like +/// [`Iterator::take()`], in order to make them finite. +/// +/// If the element type of the iterator you need does not implement `Clone`, +/// or if you do not want to keep the repeated element in memory, you can +/// instead use the [`repeat_with()`] function. +/// +/// [`repeat_with()`]: crate::iter::repeat_with +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// use std::iter; +/// +/// // the number four 4ever: +/// let mut fours = iter::repeat(4); +/// +/// assert_eq!(Some(4), fours.next()); +/// assert_eq!(Some(4), fours.next()); +/// assert_eq!(Some(4), fours.next()); +/// assert_eq!(Some(4), fours.next()); +/// assert_eq!(Some(4), fours.next()); +/// +/// // yup, still four +/// assert_eq!(Some(4), fours.next()); +/// ``` +/// +/// Going finite with [`Iterator::take()`]: +/// +/// ``` +/// use std::iter; +/// +/// // that last example was too many fours. Let's only have four fours. +/// let mut four_fours = iter::repeat(4).take(4); +/// +/// assert_eq!(Some(4), four_fours.next()); +/// assert_eq!(Some(4), four_fours.next()); +/// assert_eq!(Some(4), four_fours.next()); +/// assert_eq!(Some(4), four_fours.next()); +/// +/// // ... and now we're done +/// assert_eq!(None, four_fours.next()); +/// ``` +#[inline] +#[stable(feature = "rust1", since = "1.0.0")] +pub fn repeat(elt: T) -> Repeat { + Repeat { element: elt } +} + +/// An iterator that repeats an element endlessly. +/// +/// This `struct` is created by the [`repeat()`] function. See its documentation for more. +#[derive(Clone, Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Repeat { + element: A, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Repeat { + type Item = A; + + #[inline] + fn next(&mut self) -> Option { + Some(self.element.clone()) + } + #[inline] + fn size_hint(&self) -> (usize, Option) { + (usize::MAX, None) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for Repeat { + #[inline] + fn next_back(&mut self) -> Option { + Some(self.element.clone()) + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Repeat {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for Repeat {} diff --git a/library/core/src/iter/sources/repeat_with.rs b/library/core/src/iter/sources/repeat_with.rs new file mode 100644 index 0000000000000..44bc6890c55b5 --- /dev/null +++ b/library/core/src/iter/sources/repeat_with.rs @@ -0,0 +1,98 @@ +use crate::iter::{FusedIterator, TrustedLen}; + +/// Creates a new iterator that repeats elements of type `A` endlessly by +/// applying the provided closure, the repeater, `F: FnMut() -> A`. +/// +/// The `repeat_with()` function calls the repeater over and over again. +/// +/// Infinite iterators like `repeat_with()` are often used with adapters like +/// [`Iterator::take()`], in order to make them finite. +/// +/// If the element type of the iterator you need implements [`Clone`], and +/// it is OK to keep the source element in memory, you should instead use +/// the [`repeat()`] function. +/// +/// An iterator produced by `repeat_with()` is not a [`DoubleEndedIterator`]. +/// If you need `repeat_with()` to return a [`DoubleEndedIterator`], +/// please open a GitHub issue explaining your use case. +/// +/// [`repeat()`]: crate::iter::repeat +/// [`DoubleEndedIterator`]: crate::iter::DoubleEndedIterator +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// use std::iter; +/// +/// // let's assume we have some value of a type that is not `Clone` +/// // or which don't want to have in memory just yet because it is expensive: +/// #[derive(PartialEq, Debug)] +/// struct Expensive; +/// +/// // a particular value forever: +/// let mut things = iter::repeat_with(|| Expensive); +/// +/// assert_eq!(Some(Expensive), things.next()); +/// assert_eq!(Some(Expensive), things.next()); +/// assert_eq!(Some(Expensive), things.next()); +/// assert_eq!(Some(Expensive), things.next()); +/// assert_eq!(Some(Expensive), things.next()); +/// ``` +/// +/// Using mutation and going finite: +/// +/// ```rust +/// use std::iter; +/// +/// // From the zeroth to the third power of two: +/// let mut curr = 1; +/// let mut pow2 = iter::repeat_with(|| { let tmp = curr; curr *= 2; tmp }) +/// .take(4); +/// +/// assert_eq!(Some(1), pow2.next()); +/// assert_eq!(Some(2), pow2.next()); +/// assert_eq!(Some(4), pow2.next()); +/// assert_eq!(Some(8), pow2.next()); +/// +/// // ... and now we're done +/// assert_eq!(None, pow2.next()); +/// ``` +#[inline] +#[stable(feature = "iterator_repeat_with", since = "1.28.0")] +pub fn repeat_with A>(repeater: F) -> RepeatWith { + RepeatWith { repeater } +} + +/// An iterator that repeats elements of type `A` endlessly by +/// applying the provided closure `F: FnMut() -> A`. +/// +/// This `struct` is created by the [`repeat_with()`] function. +/// See its documentation for more. +#[derive(Copy, Clone, Debug)] +#[stable(feature = "iterator_repeat_with", since = "1.28.0")] +pub struct RepeatWith { + repeater: F, +} + +#[stable(feature = "iterator_repeat_with", since = "1.28.0")] +impl A> Iterator for RepeatWith { + type Item = A; + + #[inline] + fn next(&mut self) -> Option { + Some((self.repeater)()) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + (usize::MAX, None) + } +} + +#[stable(feature = "iterator_repeat_with", since = "1.28.0")] +impl A> FusedIterator for RepeatWith {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl A> TrustedLen for RepeatWith {} diff --git a/library/core/src/iter/sources/successors.rs b/library/core/src/iter/sources/successors.rs new file mode 100644 index 0000000000000..99f058a901a31 --- /dev/null +++ b/library/core/src/iter/sources/successors.rs @@ -0,0 +1,66 @@ +use crate::{fmt, iter::FusedIterator}; + +/// Creates a new iterator where each successive item is computed based on the preceding one. +/// +/// The iterator starts with the given first item (if any) +/// and calls the given `FnMut(&T) -> Option` closure to compute each item’s successor. +/// +/// ``` +/// use std::iter::successors; +/// +/// let powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10)); +/// assert_eq!(powers_of_10.collect::>(), &[1, 10, 100, 1_000, 10_000]); +/// ``` +#[stable(feature = "iter_successors", since = "1.34.0")] +pub fn successors(first: Option, succ: F) -> Successors +where + F: FnMut(&T) -> Option, +{ + // If this function returned `impl Iterator` + // it could be based on `unfold` and not need a dedicated type. + // However having a named `Successors` type allows it to be `Clone` when `T` and `F` are. + Successors { next: first, succ } +} + +/// An new iterator where each successive item is computed based on the preceding one. +/// +/// This `struct` is created by the [`iter::successors()`] function. +/// See its documentation for more. +/// +/// [`iter::successors()`]: successors +#[derive(Clone)] +#[stable(feature = "iter_successors", since = "1.34.0")] +pub struct Successors { + next: Option, + succ: F, +} + +#[stable(feature = "iter_successors", since = "1.34.0")] +impl Iterator for Successors +where + F: FnMut(&T) -> Option, +{ + type Item = T; + + #[inline] + fn next(&mut self) -> Option { + let item = self.next.take()?; + self.next = (self.succ)(&item); + Some(item) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + if self.next.is_some() { (1, None) } else { (0, Some(0)) } + } +} + +#[stable(feature = "iter_successors", since = "1.34.0")] +impl FusedIterator for Successors where F: FnMut(&T) -> Option {} + +#[stable(feature = "iter_successors", since = "1.34.0")] +impl fmt::Debug for Successors { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Successors").field("next", &self.next).finish() + } +} diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs index cdf742057b7b6..29364d0ce9b89 100644 --- a/library/core/src/marker.rs +++ b/library/core/src/marker.rs @@ -156,18 +156,18 @@ pub trait StructuralPartialEq { /// Required trait for constants used in pattern matches. /// /// Any type that derives `Eq` automatically implements this trait, *regardless* -/// of whether its type-parameters implement `Eq`. +/// of whether its type parameters implement `Eq`. /// -/// This is a hack to workaround a limitation in our type-system. +/// This is a hack to work around a limitation in our type system. /// -/// Background: +/// # Background /// /// We want to require that types of consts used in pattern matches /// have the attribute `#[derive(PartialEq, Eq)]`. /// /// In a more ideal world, we could check that requirement by just checking that -/// the given type implements both (1.) the `StructuralPartialEq` trait *and* -/// (2.) the `Eq` trait. However, you can have ADTs that *do* `derive(PartialEq, Eq)`, +/// the given type implements both the `StructuralPartialEq` trait *and* +/// the `Eq` trait. However, you can have ADTs that *do* `derive(PartialEq, Eq)`, /// and be a case that we want the compiler to accept, and yet the constant's /// type fails to implement `Eq`. /// @@ -176,8 +176,11 @@ pub trait StructuralPartialEq { /// ```rust /// #[derive(PartialEq, Eq)] /// struct Wrap(X); +/// /// fn higher_order(_: &()) { } +/// /// const CFN: Wrap = Wrap(higher_order); +/// /// fn main() { /// match CFN { /// CFN => {} diff --git a/library/core/src/num/f32.rs b/library/core/src/num/f32.rs index 86e6352d13215..33df175bfc54d 100644 --- a/library/core/src/num/f32.rs +++ b/library/core/src/num/f32.rs @@ -441,6 +441,32 @@ impl f32 { self.abs_private() < Self::INFINITY } + /// Returns `true` if the number is [subnormal]. + /// + /// ``` + /// #![feature(is_subnormal)] + /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32 + /// let max = f32::MAX; + /// let lower_than_min = 1.0e-40_f32; + /// let zero = 0.0_f32; + /// + /// assert!(!min.is_subnormal()); + /// assert!(!max.is_subnormal()); + /// + /// assert!(!zero.is_subnormal()); + /// assert!(!f32::NAN.is_subnormal()); + /// assert!(!f32::INFINITY.is_subnormal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(lower_than_min.is_subnormal()); + /// ``` + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[unstable(feature = "is_subnormal", issue = "79288")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + #[inline] + pub const fn is_subnormal(self) -> bool { + matches!(self.classify(), FpCategory::Subnormal) + } + /// Returns `true` if the number is neither zero, infinite, /// [subnormal], or `NaN`. /// diff --git a/library/core/src/num/f64.rs b/library/core/src/num/f64.rs index 9b1405b479f7c..b85e8deb6d22c 100644 --- a/library/core/src/num/f64.rs +++ b/library/core/src/num/f64.rs @@ -440,6 +440,32 @@ impl f64 { self.abs_private() < Self::INFINITY } + /// Returns `true` if the number is [subnormal]. + /// + /// ``` + /// #![feature(is_subnormal)] + /// let min = f64::MIN_POSITIVE; // 2.2250738585072014e-308_f64 + /// let max = f64::MAX; + /// let lower_than_min = 1.0e-308_f64; + /// let zero = 0.0_f64; + /// + /// assert!(!min.is_subnormal()); + /// assert!(!max.is_subnormal()); + /// + /// assert!(!zero.is_subnormal()); + /// assert!(!f64::NAN.is_subnormal()); + /// assert!(!f64::INFINITY.is_subnormal()); + /// // Values between `0` and `min` are Subnormal. + /// assert!(lower_than_min.is_subnormal()); + /// ``` + /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number + #[unstable(feature = "is_subnormal", issue = "79288")] + #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] + #[inline] + pub const fn is_subnormal(self) -> bool { + matches!(self.classify(), FpCategory::Subnormal) + } + /// Returns `true` if the number is neither zero, infinite, /// [subnormal], or `NaN`. /// diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index d2f36309e2daa..6037620c134f0 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -227,7 +227,6 @@ #![feature(asm)] #![feature(associated_type_bounds)] #![feature(atomic_mut_ptr)] -#![feature(bool_to_option)] #![feature(box_syntax)] #![feature(c_variadic)] #![feature(cfg_accessible)] @@ -297,7 +296,6 @@ #![feature(raw)] #![feature(raw_ref_macros)] #![feature(ready_macro)] -#![feature(refcell_take)] #![feature(rustc_attrs)] #![feature(rustc_private)] #![feature(shrink_to)] diff --git a/library/test/src/lib.rs b/library/test/src/lib.rs index 816b4d5118803..f4c07655bc4a5 100644 --- a/library/test/src/lib.rs +++ b/library/test/src/lib.rs @@ -23,7 +23,6 @@ #![cfg_attr(any(unix, target_os = "cloudabi"), feature(libc))] #![feature(rustc_private)] #![feature(nll)] -#![feature(bool_to_option)] #![feature(available_concurrency)] #![feature(internal_output_capture)] #![feature(panic_unwind)] diff --git a/src/test/ui/expr/compound-assignment/eval-order.rs b/src/test/ui/expr/compound-assignment/eval-order.rs new file mode 100644 index 0000000000000..658adae193e14 --- /dev/null +++ b/src/test/ui/expr/compound-assignment/eval-order.rs @@ -0,0 +1,76 @@ +// Test evaluation order of operands of the compound assignment operators + +// run-pass + +use std::ops::AddAssign; + +enum Side { + Lhs, + Rhs, +} + +// In the following tests, we place our value into a wrapper type so that we +// can do an element access as the outer place expression. If we just had the +// block expression, it'd be a value expression and not compile. +struct Wrapper(T); + +// Evaluation order for `a op= b` where typeof(a) and typeof(b) are primitives +// is first `b` then `a`. +fn primitive_compound() { + let mut side_order = vec![]; + let mut int = Wrapper(0); + + { + side_order.push(Side::Lhs); + int + }.0 += { + side_order.push(Side::Rhs); + 0 + }; + + assert!(matches!(side_order[..], [Side::Rhs, Side::Lhs])); +} + +// Evaluation order for `a op=b` otherwise is first `a` then `b`. +fn generic_compound + Default>() { + let mut side_order = vec![]; + let mut add_assignable: Wrapper = Wrapper(Default::default()); + + { + side_order.push(Side::Lhs); + add_assignable + }.0 += { + side_order.push(Side::Rhs); + Default::default() + }; + + assert!(matches!(side_order[..], [Side::Lhs, Side::Rhs])); +} + +fn custom_compound() { + struct Custom; + + impl AddAssign<()> for Custom { + fn add_assign(&mut self, _: ()) { + // this block purposely left blank + } + } + + let mut side_order = vec![]; + let mut custom = Wrapper(Custom); + + { + side_order.push(Side::Lhs); + custom + }.0 += { + side_order.push(Side::Rhs); + }; + + assert!(matches!(side_order[..], [Side::Lhs, Side::Rhs])); +} + +fn main() { + primitive_compound(); + generic_compound::(); + custom_compound(); +} diff --git a/src/test/ui/issues/issue-31173.stderr b/src/test/ui/issues/issue-31173.stderr index 818e004ffc8e6..d371703e29587 100644 --- a/src/test/ui/issues/issue-31173.stderr +++ b/src/test/ui/issues/issue-31173.stderr @@ -13,11 +13,13 @@ error[E0599]: no method named `collect` found for struct `Cloned, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>` | - ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL + ::: $SRC_DIR/core/src/iter/adapters/cloned.rs:LL:COL | LL | pub struct Cloned { | -------------------- doesn't satisfy `_: Iterator` -... + | + ::: $SRC_DIR/core/src/iter/adapters/take_while.rs:LL:COL + | LL | pub struct TakeWhile { | -------------------------- doesn't satisfy `<_ as Iterator>::Item = &_` | diff --git a/src/test/ui/mismatched_types/issue-36053-2.stderr b/src/test/ui/mismatched_types/issue-36053-2.stderr index 0b1fcf58e2e00..2efd37b4738a5 100644 --- a/src/test/ui/mismatched_types/issue-36053-2.stderr +++ b/src/test/ui/mismatched_types/issue-36053-2.stderr @@ -15,7 +15,7 @@ LL | once::<&str>("str").fuse().filter(|a: &str| true).count(); | doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool` | doesn't satisfy `_: FnMut<(&&str,)>` | - ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL + ::: $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL | LL | pub struct Filter { | ----------------------- doesn't satisfy `_: Iterator`