From b088f891dcef38e683655e0ca8fe73974d43d1b7 Mon Sep 17 00:00:00 2001 From: Erik Schierboom Date: Thu, 17 Oct 2024 17:27:27 +0200 Subject: [PATCH] Add `strain` exercise (#366) --- config.json | 8 ++ .../practice/strain/.docs/instructions.md | 29 ++++++ exercises/practice/strain/.meta/config.json | 19 ++++ exercises/practice/strain/.meta/example.R | 17 ++++ exercises/practice/strain/.meta/tests.toml | 52 +++++++++++ exercises/practice/strain/strain.R | 7 ++ exercises/practice/strain/test_strain.R | 90 +++++++++++++++++++ 7 files changed, 222 insertions(+) create mode 100644 exercises/practice/strain/.docs/instructions.md create mode 100644 exercises/practice/strain/.meta/config.json create mode 100644 exercises/practice/strain/.meta/example.R create mode 100644 exercises/practice/strain/.meta/tests.toml create mode 100644 exercises/practice/strain/strain.R create mode 100644 exercises/practice/strain/test_strain.R diff --git a/config.json b/config.json index d8542afd..82a50d61 100644 --- a/config.json +++ b/config.json @@ -777,6 +777,14 @@ "prerequisites": [], "difficulty": 3 }, + { + "slug": "strain", + "name": "Strain", + "uuid": "869fcbef-a5b3-4d79-bc30-e42eeb2fd319", + "practices": [], + "prerequisites": [], + "difficulty": 1 + }, { "slug": "proverb", "name": "Proverb", diff --git a/exercises/practice/strain/.docs/instructions.md b/exercises/practice/strain/.docs/instructions.md new file mode 100644 index 00000000..3469ae65 --- /dev/null +++ b/exercises/practice/strain/.docs/instructions.md @@ -0,0 +1,29 @@ +# Instructions + +Implement the `keep` and `discard` operation on collections. +Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false. + +For example, given the collection of numbers: + +- 1, 2, 3, 4, 5 + +And the predicate: + +- is the number even? + +Then your keep operation should produce: + +- 2, 4 + +While your discard operation should produce: + +- 1, 3, 5 + +Note that the union of keep and discard is all the elements. + +The functions may be called `keep` and `discard`, or they may need different names in order to not clash with existing functions or concepts in your language. + +## Restrictions + +Keep your hands off that filter/reject/whatchamacallit functionality provided by your standard library! +Solve this one yourself using other basic tools instead. diff --git a/exercises/practice/strain/.meta/config.json b/exercises/practice/strain/.meta/config.json new file mode 100644 index 00000000..985de8c8 --- /dev/null +++ b/exercises/practice/strain/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "erikschierboom" + ], + "files": { + "solution": [ + "strain.R" + ], + "test": [ + "test_strain.R" + ], + "example": [ + ".meta/example.R" + ] + }, + "blurb": "Implement the `keep` and `discard` operation on collections.", + "source": "Conversation with James Edward Gray II", + "source_url": "http://graysoftinc.com/" +} diff --git a/exercises/practice/strain/.meta/example.R b/exercises/practice/strain/.meta/example.R new file mode 100644 index 00000000..27f668e1 --- /dev/null +++ b/exercises/practice/strain/.meta/example.R @@ -0,0 +1,17 @@ +keep <- function(input, fun) { + if (is.null(input)) return(c()) + + kept <- vector(mode = mode(input)) + + for (element in input) { + if (fun(element)) { + kept[[length(kept) + 1]] <- element + } + } + + kept +} + +discard <- function(input, fun) { + keep(input, Negate(fun)) +} diff --git a/exercises/practice/strain/.meta/tests.toml b/exercises/practice/strain/.meta/tests.toml new file mode 100644 index 00000000..3a617b4a --- /dev/null +++ b/exercises/practice/strain/.meta/tests.toml @@ -0,0 +1,52 @@ +# This is an auto-generated file. +# +# Regenerating this file via `configlet sync` will: +# - Recreate every `description` key/value pair +# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications +# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion) +# - Preserve any other key/value pair +# +# As user-added comments (using the # character) will be removed when this file +# is regenerated, comments can be added via a `comment` key. + +[26af8c32-ba6a-4eb3-aa0a-ebd8f136e003] +description = "keep on empty list returns empty list" + +[f535cb4d-e99b-472a-bd52-9fa0ffccf454] +description = "keeps everything" + +[950b8e8e-f628-42a8-85e2-9b30f09cde38] +description = "keeps nothing" + +[92694259-6e76-470c-af87-156bdf75018a] +description = "keeps first and last" + +[938f7867-bfc7-449e-a21b-7b00cbb56994] +description = "keeps neither first nor last" + +[8908e351-4437-4d2b-a0f7-770811e48816] +description = "keeps strings" + +[2728036b-102a-4f1e-a3ef-eac6160d876a] +description = "keeps lists" + +[ef16beb9-8d84-451a-996a-14e80607fce6] +description = "discard on empty list returns empty list" + +[2f42f9bc-8e06-4afe-a222-051b5d8cd12a] +description = "discards everything" + +[ca990fdd-08c2-4f95-aa50-e0f5e1d6802b] +description = "discards nothing" + +[71595dae-d283-48ca-a52b-45fa96819d2f] +description = "discards first and last" + +[ae141f79-f86d-4567-b407-919eaca0f3dd] +description = "discards neither first nor last" + +[daf25b36-a59f-4f29-bcfe-302eb4e43609] +description = "discards strings" + +[a38d03f9-95ad-4459-80d1-48e937e4acaf] +description = "discards lists" diff --git a/exercises/practice/strain/strain.R b/exercises/practice/strain/strain.R new file mode 100644 index 00000000..ff2c967b --- /dev/null +++ b/exercises/practice/strain/strain.R @@ -0,0 +1,7 @@ +keep <- function(input, fun) { + +} + +discard <- function(input, fun) { + +} diff --git a/exercises/practice/strain/test_strain.R b/exercises/practice/strain/test_strain.R new file mode 100644 index 00000000..b581f595 --- /dev/null +++ b/exercises/practice/strain/test_strain.R @@ -0,0 +1,90 @@ +source("./strain.R") +library(testthat) + +test_that("Empty keep", { + input <- c() + expected <- c() + expect_equal(keep(input, \(x) x < 10), expected) +}) + +test_that("Keep everything", { + input <- c(1, 2, 3) + expected <- c(1, 2, 3) + expect_equal(keep(input, \(x) x < 10), expected) +}) + +test_that("Keep first and last", { + input <- c(1, 2, 3) + expected <- c(1, 3) + expect_equal(keep(input, \(x) x %% 2 != 0), expected) +}) + +test_that("Keep neither first nor last", { + input <- c(1, 2, 3, 4, 5) + expected <- c(2, 4) + expect_equal(keep(input, \(x) x %% 2 == 0), expected) +}) + +test_that("Keep strings", { + input <- c("apple", "zebra", "banana", "zombies", "cherimoya", "zelot") + expected <- c("zebra", "zombies", "zelot") + expect_equal(keep(input, \(x) substr(x, 1, 1) == "z"), expected) +}) + +test_that("Keep list of vectors", { + input <- list( + c(1, 2, 3), + c(5, 5, 5), + c(5, 1, 2), + c(2, 1, 2), + c(1, 5, 2), + c(2, 2, 1), + c(1, 2, 5) + ) + expected <- list(c(5, 5, 5), c(5, 1, 2), c(1, 5, 2), c(1, 2, 5)) + expect_equal(keep(input, \(x) 5 %in% x), expected) +}) + +test_that("Empty discard", { + input <- c() + expected <- c() + expect_equal(discard(input, \(x) x < 10), expected) +}) + +test_that("Discard nothing", { + input <- c(1, 2, 3) + expected <- c(1, 2, 3) + expect_equal(discard(input, \(x) x > 10), expected) +}) + +test_that("Discard first and last", { + input <- c(1, 2, 3) + expected <- c(2) + expect_equal(discard(input, \(x) x %% 2 != 0), expected) +}) + +test_that("Discard neither first nor last", { + input <- c(1, 2, 3, 4, 5) + expected <- c(1, 3, 5) + expect_equal(discard(input, \(x) x %% 2 == 0), expected) +}) + +test_that("Discard strings", { + input <- c("apple", "zebra", "banana", "zombies", "cherimoya", "zelot") + expected <- c("apple", "banana", "cherimoya") + expect_equal(discard(input, \(x) substr(x, 1, 1) == "z"), expected) +}) + +test_that("Discard list of vectors", { + input <- list( + c(1, 2, 3), + c(5, 5, 5), + c(5, 1, 2), + c(2, 1, 2), + c(1, 5, 2), + c(2, 2, 1), + c(1, 2, 5) + ) + expected <- list(c(1, 2, 3), c(2, 1, 2), c(2, 2, 1)) + expect_equal(discard(input, \(x) 5 %in% x), expected) +})