im trying to check if a given list is a subsequence of another list: here are example of lists which gives true: subseq "" "w" subseq "w" "w" subseq "ab" "cab" subseq "cb" "cab" subseq "aa" "xaxa" not (subseq "aa" "xax") not (subseq "ab" "ba") i just come to this but in some cases it gives a wrong result subseq :: Eq a => [a] -> [a] -> Bool subseq [] [] = True subseq [] ys = True subseq xs [] = False subseq (x:xs) (y:ys) = x == y || subseq xs ( 1 `drop` ys )