name: Either
description: |
  Either is a container that can be either left or right.

  Either implements functor and applicative.

functions:
- name: "Either<A, B>"
  type: "class"
  description: |
    Type of either values.

- name: "Either#match"
  type: "<K>(m: EitherMatch<A, B, K>): K"
  description: |
    Pattern matching on `Either` values. `EitherMatch<A, B, K>` must
    be a object with a `left` and `right` properties containing
    functions returning `K`.

    ```javascript
    response.match({
      right: (rating) => `User gave the rating ${rating}`,
      left: (message) => `User wrote the message: ${message}`
    });
    ```

- name: "left"
  type: "<A>(a: A): Either<A, any>"
  description: |
    Returns an `Either` that is left and contains `a`.

- name: "right"
  type: "<B>(b: B): Either<any, B>"
  description: |
    Returns an `Either` that is right and contains `b`.

- name: "isLeft"
  type: "(either: Either<any, any>): boolean"
  description: |
    Return `true` is `either` is left.

- name: "isRight"
  type: "(either: Either<any, any>): boolean"
  description: |
    Return `true` is `either` is right.


- name: "fromEither"
  type: "<A, B>(either: Either<A, B>): A | B"
  description: |
    Extracts the value from an `Either`.