[Python-Dev] RE: automatic reclaiminig of limited resources (was Re: [Python-Dev] Product iteration)

Moshe Zadka Moshe Zadka <moshez@math.huji.ac.il>
Mon, 31 Jul 2000 07:57:41 +0300 (IDT)

On Sun, 30 Jul 2000, Tim Peters wrote:

> But I don't know why we're arguing about it.  Nobody (AFAIK) has announced
> plans to take refcounting out of CPython, but that you can't *rely* on
> refcounting across Python implementations is ancient news (and a reality in
> practice since JPython).

Well, to bring this back to the original: I proposed a variant of lexical
scoping where an inner function has only a weak reference to its
surroundin environment, so that

def f(x):
	def g():
		return x
	return g


Would fail with "UnboundOuterVariable", but the more commonly used

def f(x):
	return map(lambda i,x=x: i*x, range(10))

Would turn into

def f(x):
	return map(lambda i: i*x, range(10))

And work. Guido seemed to want to simulate classes by closures <wink>,
and I tried to convince him that 

a) Python has a perfectly good class mechanism <3000 wink>
b) non-weak references would cause cycles, which would mean that the
currently working code:

def f(file):
	file = open(file)
	def g(x):
		print x

Would fail is called in a loop if GC is not called too often.

lexical-scoping-is-too-powerful-for-its-own-good-ly y'rs, Z.
Moshe Zadka <moshez@math.huji.ac.il>
There is no IGLU cabal.