Python syntax in Lisp and Scheme

[Alex Martelli]

Lulu of the Lotus-Eaters wrote:

> grzegorz at pithekos.net (Grzegorz Chrupala) wrote previously:
> |shocked at how awkward Paul Graham's "accumulator generator" snippet is
> |in Python:
> |class foo:
> |   def __init__(self, n):
> |       self.n = n
> |   def __call__(self, i):
> |       self.n += i
> |       return self.n
> 
> Me too.  The way I'd do it is probably a lot closer to the way Schemers
> would do it:
> 
>     >>> def foo(i, accum=[0]):
>     ...     accum[0]+=i
>     ...     return accum[0]
>     ...
>     >>> foo(1)
>     1
>     >>> foo(3)
>     4
> 
> Shorter, and without an awkward class.

There's an important difference: with your approach, you cannot just
instantiate multiple independent accumulators like with the other --
    a = foo(10)
    b = foo(23)
in the 'class foo' approach, just as in all of those where foo returns an
inner-function instance, a and b are now totally independent accumulator
callables -- in your approach, 'foo' itself is the only 'accumulator
callable', and a and b after these two calls are just two numbers.

Making a cookie, and making a cookie-cutter, are quite different issues.


Alex