id,summary,reporter,owner,description,type,status,priority,milestone,version,resolution,keywords,cc
15,"Add ""generalised scan""",rl,,"In any case, vector could well provide an operation like this:

{{{
cant_think_of_a_name :: Vector v a => Int -> (v a -> a) -> v a
}}}

The function would take the initialised prefix of the vector (starting with empty) and produce the next element. This would require a bit of hackery underneath but the interface would be safe and pure. Would something like this be useful?

See http://www.haskell.org/pipermail/glasgow-haskell-users/2010-May/018816.html

Note that we can't `unsafeFreeze` the vector until we are done because that would break GC for boxed vectors. Also, we can't recycle the vector because `a` could be a thunk with references to the intermediate `v a`.",enhancement,new,minor,,0.7,,,