compose

[Alex Martelli]

xam wrote:

> i've been truing to get this 'simple' code to work,
> def compose(*funcs):
> ...  if len(funcs)>1:
> ...    return lambda x:funcs[0](compose(funcs[1:])(x))
> ...  else:  return lambda x:funcs[0](x)
>>>> compose(add_5, mul_3, sub_2)(2)
> Traceback (most recent call last):
>   File "<interactive input>", line 1, in ?
>   File "<interactive input>", line 3, in <lambda>
>   File "<interactive input>", line 4, in <lambda>
> TypeError: 'tuple' object is not callable
> does anyone want to give it a shot?

The function is strange, e.g. the else clause's body should
obviously be "return funcs[0]", but the problem is not there.

Rather, you have a problem of LEVELS: function compose wants
N arguments, each of them a callable, but in your recursive
call "compose(funcs[1:])" you are passing ONE argument, a tuple
of callables.  Call "compose(*funcs[1:])" in order to fix that.


Alex