sequence in terms of fold

Author: radix

effect/fold.py

@@ -31,3 +31,9 @@ def folder(acc, element):
             return acc.on(lambda r: element.on(lambda r2: f(r, r2)))
 
     return reduce(folder, effects, _sneaky)
+
+
+def sequence(effects):
+    def folder(acc, element):
+        return acc + [element]
+    return fold_effect(folder, [], effects)

effect/test_fold.py

@@ -2,7 +2,7 @@
 import operator
 
 from effect import Effect, sync_perform
-from effect.fold import fold_effect
+from effect.fold import fold_effect, sequence
 from effect.testing import SequenceDispatcher
 
 
@@ -19,3 +19,18 @@ def test_fold_effect():
     with dispatcher.consume():
         result = sync_perform(dispatcher, eff)
     assert result == 'NilEiBeeCee'
+
+
+def test_sequence():
+    effs = [Effect('a'), Effect('b'), Effect('c')]
+    dispatcher = SequenceDispatcher([
+        ('a', lambda i: 'Ei'),
+        ('b', lambda i: 'Bee'),
+        ('c', lambda i: 'Cee'),
+    ])
+    eff = sequence(effs)
+
+    print "what the heck is sequence returning?", eff
+    with dispatcher.consume():
+        result = sync_perform(dispatcher, eff)
+    assert result == ['Ei', 'Bee', 'Cee']