Francis Girard <[EMAIL PROTECTED]> wrote:
> Thank you Nick and Steven for the idea of a more generic imerge.
You are welcome :-) [It came to me while walking the children to school!]
[snip]
> class IteratorDeiterator:
> def __init__(self, iterator):
> self._iterator = iterator.__iter__()
> self._firstVal = None ## Avoid consuming if not requested from outside
> ## Works only if iterator itself can't return None
You can use a sentinel here if you want to avoid the "can't return
None" limitation. For a sentinel you need an object your iterator
couldn't possibly return. You can make one up, eg
self._sentinel = object()
self._firstVal = self._sentinel
Or you could use self (but I'm not 100% sure that your recursive
functions wouldn't return it!)
> def __iter__(self): return self
>
> def next(self):
> valReturn = self._firstVal
> if valReturn is None:
and
if valReturn is self._sentinel:
> valReturn = self._iterator.next()
> self._firstVal = None
self._firstVal = self._sentinel
etc..
[snip more code]
Thanks for some more examples of fp-style code. I find it hard to get
my head round so its been good exercise!
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
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