Fair enough but you could do let f = map reverse in f ["ab", "cd"] IMHO the tryhaskell expose more or less only simple pure functions and I doubt that anyone

Fair enough but you could do let f = map reverse in f ["ab", "cd"] IMHO the tryhaskell expose more or less only simple pure functions and I doubt that anyone with a real interest in haskell will get any substantial out of it. However if one is completely new to programming maybe TryHaskell and these 6 short lessons have a value.