patch applied (packages/containers): specialize functions that fail in a Monad to Maybe (proposal #2309)

[Ross Paterson]

Tue Jul 22 08:48:12 PDT 2008  Ross Paterson <ross at soi.city.ac.uk>
  * specialize functions that fail in a Monad to Maybe (proposal #2309)
  
  Specialize functions signatures like
  
  	lookup :: (Monad m, Ord k) => k -> Map k a -> m a
  to
  	lookup :: (Ord k) => k -> Map k a -> Maybe a
  
  for simplicity and safety.  No information is lost, as each of these
  functions had only one use of fail, which is now changed to Nothing.

    M ./Data/IntMap.hs -46 +33
    M ./Data/IntSet.hs -30 +21
    M ./Data/Map.hs -56 +38
    M ./Data/Set.hs -11 +10

View patch online:
http://darcs.haskell.org/packages/containers/_darcs/patches/20080722154812-b47d3-4aea09e545643e2ba5cf7bbd52ab120cd6f1d2e4.gz