Either Monad and 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.

``bash


To use as standalone package

$ npm install --save akh.cont

To use as part of akh library

$ npm install --save akh
`

Usage

The EitherT and Either implement the [Fantasy Land][fl] monad, functor, and applicative functor interfaces.

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

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

#### Either.run(m), m.run()
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

`js
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(t), t.run()
Same as Either.run but for a monad transformer. Returns an Either value inside of the inner monad.


#### Either.either(m, leftCallback, rightCallback), m.either(l, r)
Perform a continuation computation m and invoke leftCallback for left results and rightCallback for right results.

`js
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(t, leftCallback, rightCallback), t.either(l, r)
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.

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

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

Contributing

Contributions are welcome.

To get started:

`bash
$ cd akh-either
$ npm install # install dev packages
$ npm test # run tests
``

[fl]: https://github.com/fantasyland/fantasy-land