Guido van Rossum wrote:
On 6/30/06, Ka-Ping Yee <python-dev@zesty.ca> wrote:
On Fri, 30 Jun 2006, Andrew Koenig wrote:
I hope Py3000 has lexical scoping a la Scheme... Me too -- that would be really nice.
That's not a very constructive proposal (especially since I don't know Scheme). Perhaps you could elaborate on what needs to change?
I believe the essence of their request for lexical scope boils down to allowing rebinding. Such code like the following is legal in Scheme: def f(x): def incr(): x = x + 1 return x def decr(): x = x - 1 return x return (incr, decr) (incr, decr) = f(1) print incr() # 2 print incr() # 3 print decr() # 2 print decr() # 1 -- FWIW, the Scheme equivalent would be something like: (define f (lambda (x) (list (lambda () (set! x (+ x 1)) x) (lambda () (set! x (- x 1)) x)))) (let ([fs (f 1)]) (let ([incr (car fs)] [decr (cadr fs)]) (display (incr)) (newline) ; 2 (display (incr)) (newline) ; 3 (display (decr)) (newline) ; 2 (display (decr)) (newline))) ; 1 As a more personal aside, I can't imagine where I would use this in any python program I have ever wrote. I actually never noticed that rebinding wasn't allowed until recently. -- Scott Dial scott@scottdial.com scodial@indiana.edu