maybe as monad
maybe as monad

ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ssaavedra/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ssaavedra/liquidhaskell,ssaavedra/liquidhaskell,ucsd-progsys/liquidhaskell,ssaavedra/liquidhaskell,ucsd-progsys/liquidhaskell,ssaavedra/liquidhaskell,ssaavedra/liquidhaskell