ABC words: Difference between revisions

m
Line 1,590:
isABC s =
isJust $
residue 'a' "bc" 'a' s
>>= residue "c" 'b' "c"
>>= elemIndex 'c'
 
residue :: CharString -> StringChar -> String -> Maybe String
residue c except c = go
where
go [] = Nothing
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