Q: Python 2.0 preliminary features?

[skaller]

Guido van Rossum wrote:
> 
> (I'm falling into the middle again.  But this is interesting.  I hope
> I haven't misunderstood Greg's description.)
> 
> Greg Ewing <greg.ewing at compaq.com> writes:
> > Under my scheme, that piece of code in itself does not create
> > a cycle. This is because a nested def does not immediately create
> > a closure; instead it creates a special "local function object"
> > which simply wraps the function. A closure is created "on
> > demand" whenever a local function object is fetched out of a
> > local variable. This is analogous to the way a bound method
> > object is created whenever a function is fetched out of a
> > class during an attribute lookup.
> 
> Hm.  I don't find it analogous, and while I agree that it's a clever
> hack to avoid cycles, I don't like it much. 

	But the real problem is simply that the inner function is
named, which can be avoided using a proper lambda. This isn't
a 'transparent' solution. However, until CPython gets a real
garbage collector (which solves the problem), a way to simultaneously
delete and return a function would be interesting: consider
changing 'del x' to an expression returning x, then:

	def make_adder():
		def adder ..
		return (del adder)

will remove adder from make_adder's stack frame, eliminating
the cycle.	

-- 
John Skaller, mailto:skaller at maxtal.com.au
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