EitherT -is:package

Type alias for ExceptT

Map over both arguments at the same time. Specialised version of bimap for EitherT.

Tag type for Either to use it as a DSum.

Convert from Either to Errors (inverse of runErrors).

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

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

Generalize Either e as MonadError e m. If the argument has form Left e, an error is produced in the monad via throwError. Otherwise, the Right a part is forwarded.

Takes an either and transforms it into something of the more generic MonadError class.

Convert Either to a DSum. Inverse of dsumToEither.

Transform Either into TomlState.

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.

Encode Either into a generalised sum type.

Transform an Either into a Validation.

>>> eitherToValidation (Right "whoop")
Success "whoop"

>>> eitherToValidation (Left "nahh")
Failure "nahh"

This function can be used to implement tryFrom with a function that returns Either. For example:

-- Avoid this:
tryFrom s = case f s of
Left e -> Left . TryFromException s . Just $ toException e
Right t -> Right t

-- Prefer this:
tryFrom = eitherTryFrom f

Convert an Either to a Maybe. A Right value becomes Just.

>>> eitherToMaybe $ Right 3
Just 3

A Left value becomes Nothing.

>>> eitherToMaybe $ Left "bye"
Nothing

Convert an Either to an Envelope.

Convert Either to Gauge, 0 meaning Right

Converts Left to ParseFailed noLoc, and a Right to ParseOk.