Mike Meyer wrote:
> Personally, I'd love a language feature that let you create a function
> that didn't evaluate arguments until they were actually used - lazy
> evaluation. That lets you write the C ?: operator as a function, for
> a start.
>
> Hmmm. No, iterators can't be used to fake it. Oh well.
if you can get some collaboration from the function itself, you can fake
anything:
def foo_default():
while 1:
print "MAKE A FOO"
yield "foo"
foo_default = foo_default()
class mydict(dict):
def setdefault(self, key, default=None):
try:
return self[key]
except KeyError:
if hasattr(default, "next"):
default = default.next()
self[key] = default
return default
d = mydict()
d["spam"] = "bacon"
print d.setdefault("spam", foo_default)
print d.setdefault("egg", foo_default)
</F>
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