Hello, I think this function might be of help in Data.List. Why I believe it would be good to have it in base: `elem` is accompanied by `findIndex` but `isInfixOf` doesn't have an accompanist. Cheers, Carlos -- | Receives a sublist and a list. It returns the index where the sublist appears in the list. For example: -- -- > findSublistIndex "abc" "abcabbc" == Just 0 -- > findSublistIndex findSublistIndex [5,6] [1..] == Just 4 -- > findSublistIndex "abbc" "abcabbc" == Just 3 -- > findSublistIndex [2,1] [2,4..10] == Nothing findSublistIndex :: (Eq a) => [a] -> [a] -> Maybe Int findSublistIndex [] _ = Nothing findSublistIndex sublist list = findSeqIndex sublist list 0 where findSeqIndex _ [] _ = Nothing findSeqIndex sublist' list'@(x:xs) i = if (sublist' `isPrefixOf` list') then Just i else findSeqIndex sublist' xs (i+1)