function operators

[Hans Nowak]

"James A. H. Skillen" wrote:
> 
> Has anyone ever wished that Python had operators defined on functions?
> For example, suppose you want the function f(x) = cos(x) + sin(x).
> You could do:
> 
>     def f(x):
>         return cos(x) + sin(x)
> 
> or
> 
>     f = lambda x: cos(x) + sin(x)
> 
> but wouldn't:
> 
>     f = cos + sin
> 
> be *much* nicer?

Here's some code that implements this behavior... I didn't test it very
well, but the general idea seems to work. Requires 2.1.

---begin---

# composable_functions.py

from __future__ import nested_scopes

class ComposableFunction:

    def __init__(self, f):
        self.f = f

    def __call__(self, *args, **kwargs):
        return apply(self.f, args, kwargs)

    def __add__(self, other):
        assert isinstance(other, ComposableFunction)
        def glue(*args):
            return self.f(*args) + other.f(*args)
        return glue
   

def test1():
    import math
    sin = ComposableFunction(math.sin)
    cos = ComposableFunction(math.cos)
    print sin(100), cos(100)

    sincos = sin + cos
    print sincos
    print sin(100) + cos(100)
    print sincos(100)
   

if __name__ == "__main__":

    test1()

---end---