> module GroupSquash ( groupSquash ) where
> import List ( groupBy )

Group-and-squasher utility function:

> groupSquash :: (a->a->Bool) -> ([a]->[a]) -> [a] -> [a]
> groupSquash eq squasher items =
>     foldr1 (++) $ map squasher $ groupBy eq items

Example usage of this sweet utility function:

< let squasher xs = case head xs of
<                     's' -> "$"
<                     'p' -> map (const 'q') xs
<                     _   -> xs
<   in
<      groupSquash (==) squasher "Mississippi"

" ==> Mi$i$iqqi