Proposal: Make intersperse lazier

[Daniel Fischer]

The current implementation of Data.List.intersperse causes a space leak 
under certain not uncommon circumstances.
Trac ticket: http://hackage.haskell.org/trac/ghc/ticket/4282
The proposed implementation,

intersperse             :: a -> [a] -> [a]
intersperse _   []      = []
intersperse sep (x:xs)  = x : go xs
  where
    go []     = []
    go (y:ys) = sep : y : go ys

changes the semantics from

intersperse (x : _|_) = _|_

to

intersperse (x : _|_) = x : _|_

apart from that, I think only the run-time behaviour is changed.

Period of discussion: Two weeks, until 30 Sep. 2010.

Cheers,
Daniel