An iterator with look-ahead

[Fredrik Lundh]

Neil Cerutti wrote:

> For use in a hand-coded parser I wrote the following simple
> iterator with look-ahead. I haven't thought too deeply about what
> peek ought to return when the iterator is exhausted. Suggestions
> are respectfully requested. As it is, you can't be sure what a
> peek() => None signifies until the next iteration unless you
> don't expect None in your sequence.

if you're doing simple parsing on an iterable, it's easier and more efficient
to pass around the current token and the iterator's next method:

http://online.effbot.org/2005_11_01_archive.htm#simple-parser-1

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