Left factorials: Difference between revisions

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@@ Line 2,679: / Line 2,679: @@
 {{Trans|Haskell}}
-<lang python>"""Left factorials"""
+<lang python>'''Left factorials'''
 from itertools import (accumulate, chain, count, islice)
@@ Line 2,687: / Line 2,687: @@
 # leftFact :: [Integer]
 def leftFact():
-    '''Left factorial series defined in terms of the factorial series'''
+    '''Left factorial series defined in terms
+       of the factorial series.
-    return scanl(add)(0)(
-        fact()
+    '''
+    return accumulate(
+        chain([0], fact()), add
     )
@@ Line 2,695: / Line 2,697: @@
 # fact :: [Integer]
 def fact():
-    '''Factorial series – a non-finite list'''
+    '''The factorial series.
+    '''
-    return scanl(mul)(1)(
-        enumFrom(1)
+    return accumulate(
+        chain([1], count(1)), mul
     )
-# TEST ----------------------------------------------------
+# ------------------------- TEST -------------------------
 # main :: IO ()
 def main():
@@ Line 2,725: / Line 2,728: @@
-# GENERIC -------------------------------------------------
+# ----------------------- GENERIC ------------------------
 # compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
@@ Line 2,731: / Line 2,734: @@
     '''Function composition.'''
     return lambda f: lambda x: g(f(x))
-# enumFrom :: Enum a => a -> [a]
-def enumFrom(x):
-    '''A non-finite stream of enumerable values,
-       starting from the given value.'''
-    return count(x) if isinstance(x, int) else (
-        map(chr, count(ord(x)))
-    )
 # scanl :: (b -> a -> b) -> b -> [a] -> [b]
 def scanl(f):
-    '''scanl is like reduce, but returns a succession of
+    '''scanl is like reduce, but defines a succession of
-       intermediate values, building from the left.'''
+       intermediate values, building from the left.
+    '''
-    return lambda a: lambda xs: (
+    def go(a):
-        accumulate(chain([a], xs), f)
-    )
+        def g(xs):
+            return accumulate(chain([a], xs), f)
+        return g
+    return go