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--!!! ds025 -- overloaded assoc -- AbsBinds
module Util where
ehead xs loc | null xs = error ("4"++loc)
| True = head xs
assoc key lst loc
= if (null res) then error ("1"++loc++"2"++(show key))
else (ehead res "3")
where res = [ val | (key',val) <- lst, key==key']
assocMaybe :: (Eq a) => a -> [(a,b)] -> Maybe b
assocMaybe key lst
= if (null res) then Nothing else (Just (head res))
where res = [ val | (key',val) <- lst, key==key']
data Maybe a = Just a | Nothing deriving ()
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