Merge pull request #33 from fink-lang/fold-with-initial-ctx

feat(iter): add support for initial shared accu for fold_ac

Author: kollhof

package-lock.json

@@ -20,7 +20,7 @@ sort = _sort_
 
 
 
-fold = fn initial, fold_fn=initial:
+fold = fn initial, fold_fn:
   foldr = fn iterable, prev, ctx, fold_fn:
     [item, rest, next_ctx=ctx] = _next_ iterable, ctx
     match rest:
@@ -31,13 +31,14 @@ fold = fn initial, fold_fn=initial:
 
   fn items:
     it = _iter_ items
-    [init, ff] = match initial:
-      fold_fn: [, fold_fn]
-      else: [initial, fold_fn]
-    foldr it, init, _, ff
+    match true:
+      is_fn fold_fn:
+        foldr it, initial, _, fold_fn
+      else:
+        foldr it, _, _, initial
 
 
-fold_ac = fn initial, fold_fn=initial:
+fold_ac = fn initial, ctx, fold_fn:
   foldr = fn iterable, prev, acc, ctx, fold_fn:
     [item, rest, f_ctx=ctx] = _next_ iterable, ctx
     match rest:
@@ -48,10 +49,16 @@ fold_ac = fn initial, fold_fn=initial:
 
   fn items:
     it = _iter_ items
-    [init, ff] = match initial:
-      fold_fn: [, fold_fn]
-      else: [initial, fold_fn]
-    foldr it, init, _, _, ff
+    uses_ctx = is_fn fold_fn
+
+    acc_ctx_fold_fn = match true:
+      is_fn fold_fn: [ , ctx, fold_fn]
+      else: [ , , ctx]
+
+    [result, next_ctx] = foldr it, initial, ...acc_ctx_fold_fn
+    match true:
+      uses_ctx: [result, next_ctx]
+      else: result
 
 
 
@@ -109,6 +116,7 @@ filter_ac = fn filter_fn:
 
 
 
+
 while = fn while_fn:
   next_fn = fn iterable, ctx:
     [item, rest, next_ctx=ctx] = _next_ iterable, ctx

src/iter.fnk

@@ -24,7 +24,7 @@ expect_iter = fn actual, expectation:
 describe 'fold', fn:
   it 'folds items', fn:
     expect
-      '123' | fold_ fn item, prev='':
+      '123' | fold_ '', fn item, prev:
         '${item}${prev}'
       to_equal
         '321'
@@ -36,22 +36,37 @@ describe 'fold', fn:
       to_equal
         'foobar'
 
+  it 'folds without initial', fn:
+    expect
+      '123' | fold_ fn item, prev='':
+        '${item}${prev}'
+      to_equal
+        '321'
+
 
 describe fold_ac, fn:
   it 'folds items with accu', fn:
     expect
-      'abc' | fold_ac fn item, prev='', acc=0:
+      'abc' | fold_ac '', fn item, prev, acc=0:
         ['${prev},${item}${acc}', acc + 1]
       to_equal
-        [',a0,b1,c2', ]
+        ',a0,b1,c2'
 
-  it 'folds items with shared accu', fn:
+  it 'folds with shared accu', fn:
     expect
-      pipe 'abc':
-        fold_ac '.', fn item, prev, , cntr=0:
+      pipe '123':
+        fold_ac '.', 0, fn item, prev, , cntr:
           ['${prev}${item}', , cntr + 1]
       to_equal
-        ['.abc', 3]
+        ['.123', 3]
+
+  it 'folds empty with shared accu', fn:
+    expect
+      pipe '':
+        fold_ac '', 0, fn item, prev, , cntr:
+          ['${prev}${item}', , cntr + 1]
+      to_equal
+        ['', 0]
 
 
 
@@ -333,9 +348,9 @@ describe flatten, fn:
     expect
       pipe 'abc':
         map_ac fn item, , ctx=0:
-          [[ctx, item],, ctx + 1]
+          [[ctx, item], , ctx + 1]
         flatten
-        fold_ fn it, out=[], , ctx:
+        fold_ [], fn it, out, , ctx:
           [...out, '${it}${ctx}']
       to_equal
         ["01", "a1", "12", "b2", "23", "c3"]
@@ -747,12 +762,12 @@ describe 'performance', fn:
         zip ?, count 1000
         map fn [item, cntr]: {cntr, item}
         filter fn {cntr}: cntr % 2 == 0
-        fold_ac 0, fn _, c=0: [c + 1]
-        fn [a]: a
+        fold_ac 0, fn _, c: [c + 1]
+
 
     t2 = fn:
       pipe range 100:
-        fold_ fn: t1 _
+        fold_ 0, fn: t1 _
 
     expect
       t2 _