JuliaLang/julia — pull request #2185 by WestleyArgentum (2013-02-05 01:04:10+00:00)
Title: memory efficient filter(Function, Associative)

I don't like that this relies on the Associative type having a default constructor...

The previous version only counted on `copy`, which means that a composite type that provided the Associative interface but could not be constructed by default (maybe had more things dynamically added) could still work...

So I'm not sure if this is a good idea.