:: Either a b -> Maybe b -package:from-sum

Given an Either, convert it to a Maybe, where Left becomes Nothing.

\x -> eitherToMaybe (Left x) == Nothing
\x -> eitherToMaybe (Right x) == Just x

Maybe get the Right side of an Either.

rightToMaybe ≡ either (const Nothing) Just

Using Control.Lens:

rightToMaybe ≡ preview _Right
rightToMaybe x ≡ x^?_Right

>>> rightToMaybe (Left 12)
Nothing

>>> rightToMaybe (Right 12)
Just 12

Suppress the Left value of an Either

Transform an Either value into a Maybe value. Right is mapped to Just and Left is mapped to Nothing. The value inside Left is lost.

Safe projection from Right.

maybeRight (Right b) = Just b
maybeRight Left{}    = Nothing

A fromRight that fails in the Maybe monad

Maps right part of Either to Maybe.

>>> rightToMaybe (Left True)
Nothing

>>> rightToMaybe (Right "aba")
Just "aba"

Turn Right into Just and Left into Nothing.

To prevent a dependency on package errors

Converts an Either to a Maybe.

Lifts an Either e into Monad m with effect Throw e

Return value on the Right and fail otherwise. Lifted version of expectRight.