Match behaviour of chunk with tidal, add fastChunk for old strudel be…

…haviour. Also adds repeatCycles. fixes #689

packages/core/pattern.mjs

@@ -2100,25 +2100,50 @@ export const { iterBack, iterback } = register(['iterBack', 'iterback'], functio
   return _iter(times, pat, true);
 });
 
+/**
+ * Repeats each cycle the given number of times.
+ * @name repeatCycles
+ * @memberof Pattern
+ * @returns Pattern
+ * @example
+ * note(irand(12).add(34)).segment(4).repeatCycles(2).s("gm_acoustic_guitar_nylon")
+ */
+const _repeatCycles = function (n, pat) {
+  return slowcat(...Array(n).fill(pat));
+}
+
+const { repeatCycles } = register('repeatCycles', _repeatCycles);
+
 /**
  * Divides a pattern into a given number of parts, then cycles through those parts in turn, applying the given function to each part in turn (one part per cycle).
  * @name chunk
+ * @synonyms slowChunk, slowchunk
  * @memberof Pattern
  * @returns Pattern
  * @example
  * "0 1 2 3".chunk(4, x=>x.add(7)).scale('A minor').note()
  */
-const _chunk = function (n, func, pat, back = false) {
+const _chunk = function (n, func, pat, back = false, fast = false) {
   const binary = Array(n - 1).fill(false);
   binary.unshift(true);
-  const binary_pat = _iter(n, sequence(...binary), back);
+  // Invert the 'back' because we want to shift the pattern forwards,
+  // and so time backwards
+  const binary_pat = _iter(n, sequence(...binary), !back);
+  if (!fast) {
+    pat = pat.repeatCycles(n);
+  }
   return pat.when(binary_pat, func);
 };
 
-export const chunk = register('chunk', function (n, func, pat) {
-  return _chunk(n, func, pat, false);
+const {chunk, slowchunk, slowChunk} = register(['chunk', 'slowchunk', 'slowChunk'], function (n, func, pat) {
+  return _chunk(n, func, pat, false, false);
 });
 
+const {fastchunk, fastChunk} = register(['fastchunk', 'fastChunk'], function (n, func, pat) {
+  return _chunk(n, func, pat, false, true);
+});
+
+
 /**
  * Like `chunk`, but cycles through the parts in reverse order. Known as chunk' in tidalcycles
  * @name chunkBack

packages/core/test/pattern.test.mjs

@@ -1003,4 +1003,20 @@ describe('Pattern', () => {
       );
     });
   });
+  describe('chunk', () => {
+    it('Processes each cycle of the source pattern multiple times, once for each chunk', () => {
+      expect(sequence(0, 1, 2, 3).slow(2).chunk(2, add(10)).fast(4).firstCycleValues).toStrictEqual([ 10, 1, 0, 11, 12, 3, 2, 13 ])
+    });
+  });
+  describe('fastChunk', () => {
+    it('Unlike chunk, cycles of the source pattern proceed cycle-by-cycle', () => {
+      expect(sequence(0, 1, 2, 3).slow(2).fastChunk(2, add(10)).fast(4).firstCycleValues).toStrictEqual([ 10,1,2,13,10,1,2,13 ])
+    });
+  });
+  describe('repeatCycles', () => {
+    it('Repeats each cycle of the source pattern the given number of times', () => {
+      expect(slowcat(0, 1).repeatCycles(2).fast(6).firstCycleValues).toStrictEqual([ 0,0,1,1,0,0 ])
+    });
+  });
+
 });

test/__snapshots__/examples.test.mjs.snap

@@ -1087,17 +1087,17 @@ exports[`runs examples > example "chunk" example index 0 1`] = `
   "[ 1/2 → 3/4 | note:C4 ]",
   "[ 3/4 → 1/1 | note:D4 ]",
   "[ 1/1 → 5/4 | note:A3 ]",
-  "[ 5/4 → 3/2 | note:B3 ]",
+  "[ 5/4 → 3/2 | note:B4 ]",
   "[ 3/2 → 7/4 | note:C4 ]",
-  "[ 7/4 → 2/1 | note:D5 ]",
+  "[ 7/4 → 2/1 | note:D4 ]",
   "[ 2/1 → 9/4 | note:A3 ]",
   "[ 9/4 → 5/2 | note:B3 ]",
   "[ 5/2 → 11/4 | note:C5 ]",
   "[ 11/4 → 3/1 | note:D4 ]",
   "[ 3/1 → 13/4 | note:A3 ]",
-  "[ 13/4 → 7/2 | note:B4 ]",
+  "[ 13/4 → 7/2 | note:B3 ]",
   "[ 7/2 → 15/4 | note:C4 ]",
-  "[ 15/4 → 4/1 | note:D4 ]",
+  "[ 15/4 → 4/1 | note:D5 ]",
 ]
 `;
 
@@ -1108,17 +1108,17 @@ exports[`runs examples > example "chunkBack" example index 0 1`] = `
   "[ 1/2 → 3/4 | note:C4 ]",
   "[ 3/4 → 1/1 | note:D4 ]",
   "[ 1/1 → 5/4 | note:A3 ]",
-  "[ 5/4 → 3/2 | note:B4 ]",
+  "[ 5/4 → 3/2 | note:B3 ]",
   "[ 3/2 → 7/4 | note:C4 ]",
-  "[ 7/4 → 2/1 | note:D4 ]",
+  "[ 7/4 → 2/1 | note:D5 ]",
   "[ 2/1 → 9/4 | note:A3 ]",
   "[ 9/4 → 5/2 | note:B3 ]",
   "[ 5/2 → 11/4 | note:C5 ]",
   "[ 11/4 → 3/1 | note:D4 ]",
   "[ 3/1 → 13/4 | note:A3 ]",
-  "[ 13/4 → 7/2 | note:B3 ]",
+  "[ 13/4 → 7/2 | note:B4 ]",
   "[ 7/2 → 15/4 | note:C4 ]",
-  "[ 15/4 → 4/1 | note:D5 ]",
+  "[ 15/4 → 4/1 | note:D4 ]",
 ]
 `;
 
@@ -3528,6 +3528,27 @@ exports[`runs examples > example "release" example index 0 1`] = `
 ]
 `;
 
+exports[`runs examples > example "repeatCycles" example index 0 1`] = `
+[
+  "[ 0/1 → 1/4 | note:42 s:gm_acoustic_guitar_nylon ]",
+  "[ 1/4 → 1/2 | note:38 s:gm_acoustic_guitar_nylon ]",
+  "[ 1/2 → 3/4 | note:35 s:gm_acoustic_guitar_nylon ]",
+  "[ 3/4 → 1/1 | note:38 s:gm_acoustic_guitar_nylon ]",
+  "[ 1/1 → 5/4 | note:42 s:gm_acoustic_guitar_nylon ]",
+  "[ 5/4 → 3/2 | note:38 s:gm_acoustic_guitar_nylon ]",
+  "[ 3/2 → 7/4 | note:35 s:gm_acoustic_guitar_nylon ]",
+  "[ 7/4 → 2/1 | note:38 s:gm_acoustic_guitar_nylon ]",
+  "[ 2/1 → 9/4 | note:42 s:gm_acoustic_guitar_nylon ]",
+  "[ 9/4 → 5/2 | note:36 s:gm_acoustic_guitar_nylon ]",
+  "[ 5/2 → 11/4 | note:39 s:gm_acoustic_guitar_nylon ]",
+  "[ 11/4 → 3/1 | note:41 s:gm_acoustic_guitar_nylon ]",
+  "[ 3/1 → 13/4 | note:42 s:gm_acoustic_guitar_nylon ]",
+  "[ 13/4 → 7/2 | note:36 s:gm_acoustic_guitar_nylon ]",
+  "[ 7/2 → 15/4 | note:39 s:gm_acoustic_guitar_nylon ]",
+  "[ 15/4 → 4/1 | note:41 s:gm_acoustic_guitar_nylon ]",
+]
+`;
+
 exports[`runs examples > example "reset" example index 0 1`] = `
 [
   "[ 0/1 → 1/4 | s:hh ]",