maybeToEither -package:from-sum

Given a Maybe, convert it to an Either, providing a suitable value for the Left should the value be Nothing.

\a b -> maybeToEither a (Just b) == Right b
\a -> maybeToEither a Nothing == Left a

Converts a Maybe value to an Either value, using the supplied parameter as the Left value if the Maybe is Nothing. This function can be interpreted as:

maybeToEither :: e -> Maybe a -> Either e a

Its definition is given as it is so that it can be used in the Error and related monads.

Transform a Maybe value into an Either value. Just is mapped to Right and Nothing is mapped to Left. Default Left required.

Convert Maybe to Either e, given an error e for the Nothing case.