Le samedi 30 avril 2011 à 08:59 -0700, Tom Bachmann a écrit :
> This is roughly what I had in mind:
> [Everything is fake here, to only thing that is supposed to be
> illustrated is how assumptions get cleared up when their objects
> vanish.]
>
> import weakref
>
> class Assumption(object):
> pass
>
> class AssumePositive(Assumption):
>
> def __init__(self, x):
> self.var = weakref.ref(x, self.cb)
>
> def cb(self, var):
> if self.callback:
> self.callback(self)
>
> def __str__(self):
> return str(self.var) + ' > 0'
>
> class Symbol(object):
> def __init__(self, name):
> self.name = name
>
> def __str__(self):
> return str(self.name)
>
> assumptions = {}
>
> def remove_assumption(wr):
> print 'removing assumption', assumptions[wr]
> del assumptions[wr]
>
> N = 0
> def assume(a):
> global N
> print 'adding assumption', a, 'as', N
> assumptions[a] = N
> a.callback = remove_assumption
> N += 1
>
> def test2():
> x = Symbol('y')
> assume(AssumePositive(x))
> print assumptions
> print 'leaving test2'
>
> def test():
> x = Symbol('x')
> assume(AssumePositive(x))
> print assumptions
> print 'entering test2'
> test2()
> print assumptions
> print 'leaving test'
>
> test()
>
I don't see how this is in any way better than storing the assumptions
on the object. For instance, assume(AssumePositive(x + y)) won't work
properly. And it's not clear how assumptions can be retrieved.
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