haskell - Why is there not a funtion `quit = fail ""` for MaybeT? -
looking @ source code of fail in maybet instance of monad : instance (monad m) => monad (maybet m) fail _ = maybet (return nothing) it's clear argument of fail not used. why isn't there cleaner function quit :: maybet m () saves typing fail "" everytime? or missing something? that mzero is maybet 's monadplus instance (except type more general 1 gave: maybet instance, have mzero :: monad m => maybet m a ).