[Python-3000] Efficient LC's which don't leak the iteration variables (was Re: Py3k release schedule worries) (original) (raw)
Nick Coghlan ncoghlan at gmail.com
Thu Dec 21 09:56:29 CET 2006
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Greg Ewing wrote:
Jim Jewett wrote:
Knowing which i's to rename strikes me as tricky, It shouldn't be too hard if you approach it the right way. One way would be to temporarily change the symbol table entry for the loop var when compiling the loop body and any nested functions so that it refers to a different slot in the locals.
The more I think about it, the more I think it will be simplest to tackle the list comprehension as a 'pseudo-scope'. These would still effectively create new scopes, but because they're executed immediately, they can get away with borrowing the local namespace and execution frame of the current function rather than running independently.
The compiler already has to keep track of which scope it is in order to handle closure variables - the idea would be to add a mechanism to the scope stack whereby each entry could either be a 'real' scope (actual separate local namespace) or a 'virtual' scope (names in the scope are remapped to start with an appropriate numeric prefix in the current local namespace).
Georg, if you want to tackle this, go ahead. Otherwise, I'll look into it over the next couple of weeks.
Cheers, Nick.
-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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