akh.either

Either monad transformer for Akh Javascript Monad library

The EitherT transformer, EitherT, adds either values to a monad. The base type, Either, provides either computation logic on its own.

The EitherT and Either is a monad, functor, and applicative functor.

// Either monad
require('akh.either').Either
require('akh').Either

// Either monad transformer
require('akh.either').EitherT
require('akh').EitherT

Running

Either::run(m)

Perform a continuation computation m and get the result as an Either. Either has a value property plus either a left or right property to show its type

const Either = requre('akh.either').Either

Either.run(Either.right(4)) === { right: true, value: 4 }
Either.run(Either.left(-1)) === { left: true, value: -1 }

EitherT::run(m)

Same as Either.run but for a monad transformer. Returns an Either value inside of the inner monad.

Either::either(m, leftCallback, rightCallback)

Perform a continuation computation m and invoke leftCallback for left results and rightCallback for right results.

const Either = requre('akh.either').Either

const c = Either.of(3)
        .map((x) => -x);

Either.either(c, console.error, console.log); // logs: -3

EitherT::either(m, leftCallback, rightCallback)

Same as Either::either but for transformed types

Either Interface

Either.right(x)

EitherT(m).right(x)

Construct a right value.

This is the same as of since right values are considered the normal case.

Either.left(x)

EitherT(m).left(x)

Construct a left value.

Left values are considered the error case and do not have map or chain applied to them.

const c = Either.left(3)
        .map((x) => -x);

Either.either(c, console.error, console.log); // errors: 3

Changelog

0.0.0 - September 1, 2016

• Initial release.