Closures python,scheme,ruby

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paolo veronelli <paolo_veronelli at yahoo.it> wrote in message news:<mailman.250.1089623585.5135.python-list at python.org>...
> I've a vague idea of the differences,I don't know scheme anyway.
> 
> I'd like to see an example to show what is missing in python about 
> closures and
> possibly understand if ruby is better in this sense.
> 
> Iuse ruby and python in parallel for my job just to learn them and their 
> differences and python is shorter and cleaner ,but i feel it's missing 
> something,
> in closures.Any hints?
> 
> 				grazie Paolino

Python is cleaner but not shorter ;) I don't know about closures in Ruby,
the basic difference between Python and Scheme is that Python
closures are read-only, whereas Scheme closures are read-write
(Scheme has a set! primitive). Here is an example:

(define (outer)
  (let ((x 1))
    (lambda () (set! x 2) x)))

((outer))
2

You cannot do that in Python, unless you use ugly tricks with mutable objects.


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