September Morn Update

Task/Function-composition/Python/function-composition-3.py

@@ -0,0 +1,36 @@
+from math import (acos, cos, asin, sin)
+
+
+# compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
+def compose(g, f):
+    '''Right to left function composition.'''
+    return lambda x: g(f(x))
+
+
+# main :: IO ()
+def main():
+    '''Test'''
+
+    print(list(map(
+        lambda f: f(0.5),
+        zipWith(compose)(
+            [sin, cos, lambda x: x ** 3.0]
+        )([asin, acos, lambda x: x ** (1 / 3.0)])
+    )))
+
+
+# GENERIC FUNCTIONS ---------------------------------------
+
+
+# zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
+def zipWith(f):
+    '''A list constructed by zipping with a
+       custom function, rather than with the
+       default tuple constructor.'''
+    return lambda xs: lambda ys: (
+        map(f, xs, ys)
+    )
+
+
+if __name__ == '__main__':
+    main()

Task/Function-composition/Python/function-composition-4.py

@@ -0,0 +1,43 @@
+from functools import reduce
+from numbers import Number
+import math
+
+
+def main():
+    '''Test'''
+
+    f = composeList([
+        lambda x: x / 2,
+        succ,
+        math.sqrt
+    ])
+
+    print(
+        f(5)
+    )
+
+
+# GENERIC FUNCTIONS ---------------------------------------
+
+
+# composeList :: [(a -> a)] -> (a -> a)
+def composeList(fs):
+    '''Composition, from right to left,
+       of a series of functions.'''
+    return lambda x: reduce(
+        lambda a, f: f(a),
+        fs[::-1],
+        x
+    )
+
+
+# succ :: Enum a => a -> a
+def succ(x):
+    '''The successor of a value. For numeric types, (1 +).'''
+    return 1 + x if isinstance(x, Number) else (
+        chr(1 + ord(x))
+    )
+
+
+if __name__ == '__main__':
+    main()