Proposal #2659: Add sortOn and friends to Data.List

roconnor at roconnor at
Thu Oct 9 14:25:49 EDT 2008

>>     groupOn         :: Eq b => (a -> b) -> [a] -> [[a]]

I don't know how other people use groupBy, but I'm almost always looking 
for something of the the type

Eq b => (a -> b) -> [a] -> [(b,[a])]

I just bring this up as something to think about.  It is easy to construct 
from groupOn, however it is almost as easy to construct from groupBy.  So 
groupOn doesn't really gain me much. :)

Russell O'Connor                                      <>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''

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