Data commit

Task/Repeat/Python/repeat-1.py

@@ -0,0 +1,9 @@
+#!/usr/bin/python
+def repeat(f,n):
+  for i in range(n):
+    f();
+
+def procedure():
+  print("Example");
+
+repeat(procedure,3); #prints "Example" (without quotes) three times, separated by newlines.

Task/Repeat/Python/repeat-2.py

@@ -0,0 +1,99 @@
+'''Application of a given function, repeated N times'''
+
+from itertools import repeat
+from functools import reduce
+from inspect import getsource
+
+
+# applyN :: Int -> (a -> a) -> a -> a
+def applyN(n):
+    '''n compounding applications of the supplied
+       function f. Equivalent to Church numeral n.
+    '''
+    def go(f):
+        return lambda x: reduce(
+            lambda a, g: g(a), repeat(f, n), x
+        )
+    return lambda f: go(f)
+
+
+# MAIN ----------------------------------------------------
+def main():
+    '''Tests - compounding repetition
+       of function application.
+    '''
+    def f(x):
+        return x + 'Example\n'
+
+    def g(x):
+        return 2 * x
+
+    def h(x):
+        return 1.05 * x
+
+    print(
+        fTable(__doc__ + ':')(
+            lambda fx: '\nRepeated * 3:\n (' + (
+                getsource(fst(fx)).strip() + ')(' +
+                repr(snd(fx)) + ')'
+            )
+        )(str)(
+            liftA2(applyN(3))(fst)(snd)
+        )([(f, '\n'), (g, 1), (h, 100)])
+    )
+
+
+# GENERIC -------------------------------------------------
+
+# compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
+def compose(g):
+    '''Right to left function composition.'''
+    return lambda f: lambda x: g(f(x))
+
+
+# fst :: (a, b) -> a
+def fst(tpl):
+    '''First member of a pair.'''
+    return tpl[0]
+
+
+# liftA2 :: (a0 -> b -> c) -> (a -> a0) -> (a -> b) -> a -> c
+def liftA2(op):
+    '''Lift a binary function to a composition
+       over two other functions.
+       liftA2 (*) (+ 2) (+ 3) 7 == 90
+    '''
+    def go(f, g):
+        return lambda x: op(
+            f(x)
+        )(g(x))
+    return lambda f: lambda g: go(f, g)
+
+
+# snd :: (a, b) -> b
+def snd(tpl):
+    '''Second member of a pair.'''
+    return tpl[1]
+
+
+# fTable :: String -> (a -> String) ->
+#                     (b -> String) -> (a -> b) -> [a] -> String
+def fTable(s):
+    '''Heading -> x display function -> fx display function ->
+                     f -> xs -> tabular string.
+    '''
+    def go(xShow, fxShow, f, xs):
+        ys = [xShow(x) for x in xs]
+        w = max(map(len, ys))
+        return s + '\n' + '\n'.join(map(
+            lambda x, y: y.rjust(w, ' ') + ' -> ' + fxShow(f(x)),
+            xs, ys
+        ))
+    return lambda xShow: lambda fxShow: lambda f: lambda xs: go(
+        xShow, fxShow, f, xs
+    )
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()