On 7 Aug 2009, at 15:08 , ilya wrote:
I'd like to use this syntax only in situations of PEP 312, that is, where a colon is prohibited by current grammar. In those situations, writing _: is also prohibited by current grammar so it will be parsed unambiguously.
The examples you quoted will not change under my idea, but ``x = (_:_*2)`` would be possible as an alternative. Note that I would be against being able to use ``x = _:_*2``. I think it's better to require either lambda keyword or parentheses for the RHS of the assignment as colon has a well-defined meaning as starting an indented block unless it's inside some brackets.
It's not much of a gain though, some kind of currying for operators might be a more general idea for those cases. Or simply a better lambda syntax (Haskell has a pretty cool one for what it's worth, but it might conflict with the EOL escape thing), but as far as I know previous discussions on the subject have either failed to come up with a viable syntax or failed to get the approval of the community or BDFL.