Proposal #1464: add dropPrefix to Data.List

[Stefan Holdermans]

Ian, Chris,

>    dropPrefix :: (Monad m, Eq a) => [a] -> [a] -> m [a]
>    dropPrefix [] ys = return ys
>    dropPrefix (x:xs) (y:ys)
>     | x == y = dropPrefix xs ys
>    dropPrefix _ _ = fail "parse error"

I also would like a monadic variant better (cf. Data.Map.lookup).  
However, I'd name it differently---not sure how, though---and reserve  
dropPrefix for

   dropPrefix          :: (Eq a) => [a] -> [a] -> [a]
   dropPrefix prefix l =  go prefix l where
     go (x : xs) (y : ys) | x == y = go xs ys
     go []       ys                = ys
     go _        _                 = l

which, to me, at least, seems more in line with drop and dropWhile.

Just my two cents, though.

Cheers,

   Stefan