tests and tweaks, and add chunkBackInto

packages/core/pattern.mjs

@@ -2530,7 +2530,21 @@ export const { fastchunk, fastChunk } = register(
  */
 export const { chunkinto, chunkInto } = register(['chunkinto', 'chunkInto'],
   function (n, func, pat) {
-    return pat.into(fastcat(true, ...Array(n - 1).fill(false)).iterback(n), func);
+    return pat.into(fastcat(true, ...Array(n - 1).fill(false))._iterback(n), func);
+  });
+
+/**
+ * Like `chunkInto`, but moves backwards through the chunks.
+ * @name chunkBackInto
+ * @synonym chunkbackinto
+ * @memberof Pattern
+ * @example
+ * sound("bd sd ht lt bd - cp lt").chunkInto(4, hurry(2))
+ *   .bank("tr909")
+ */
+export const { chunkbackinto, chunkBackInto } = register(['chunkbackinto', 'chunkBackInto'],
+  function (n, func, pat) {
+    return pat.into(fastcat(true, ...Array(n - 1).fill(false))._iter(n)._early(1), func);
   });
 
 // TODO - redefine elsewhere in terms of mask

packages/core/test/pattern.test.mjs

@@ -1278,7 +1278,7 @@ describe('Pattern', () => {
         fastcat('a', 'b', 'a', 'b', 'c', 'c', 'd', 'd')
       )
     })
-  })
+  });
   describe('into', () => {
     it('applies a function to subcycles of a pattern', () => {
       sameFirst(
@@ -1286,12 +1286,19 @@ describe('Pattern', () => {
         fastcat('a', 'a', 'b', 'b', 'c', 'd', 'c', 'd')
       )
     })
-  }),
-    describe('chunkinto', () => {
-      it('chunks into subcycles', () => {
-        sameFirst(fastcat('a', 'b', 'c').chunkInto(3, fast(2)).fast(3),
-          fastcat(fastcat('a', 'a'), 'b', 'c', 'a', fastcat('b', 'b'), 'c', 'a', 'b', fastcat('c', 'c'))
-        )
-      })
+  });
+  describe('chunkinto', () => {
+    it('chunks into subcycles', () => {
+      sameFirst(fastcat('a', 'b', 'c').chunkInto(3, fast(2)).fast(3),
+        fastcat(fastcat('a', 'a'), 'b', 'c', 'a', fastcat('b', 'b'), 'c', 'a', 'b', fastcat('c', 'c'))
+      )
     })
+  });
+  describe('chunkbackinto', () => {
+    it('chunks into subcycles backwards', () => {
+      sameFirst(fastcat('a', 'b', 'c').chunkBackInto(3, fast(2)).fast(3),
+        fastcat('a', 'b', fastcat('c', 'c'), 'a', fastcat('b', 'b'), 'c', fastcat('a', 'a'), 'b', 'c')
+      )
+    })
+  });
 });