@typed-f/maybe

[![NPM Version][maybe-npm-version-badge]][maybe-npm]
[repo-circleci-badge]: https://img.shields.io/circleci/project/github/Ailrun/typed-f/master.svg?logo=circleci
[![Known Vulnerabilities][maybe-snyk-badge]][maybe-snyk]
[![Supported TypeScript Version][repo-supported-typescript-badge]][supported-typescript]
[![PRs Welcome][prs-welcome-badge]][prs-welcome]

[![Watch on GitHub][repo-github-watch-badge]][repo-github-watch]
[![Star on GitHub][repo-github-star-badge]][repo-github-star]

Partial type for Typed-F

Installation

``shell


for NPM>=5

npm install @typed-f/maybe

or

npm i @typed-f/maybe

for NPM<5

npm install --save @typed-f/maybe

or

npm i -S @typed-f/maybe
`

APIs

This package includes type definition for Maybe type, which is an union type of Just and Nothing.
This package also includes their methods and some utility functions for them.

$3

- Maybe
- Just
- Nothing

$3

- isJust(this: Maybe): this is Just
Checks whether this is Just or not. You can use this with if statement like following code.
`typescript
declare const m: Maybe;

if (m.isJust()) {
// Now m is Just
console.log(m.value.toFixed(4));
}
`
- isNothing(this: Maybe): this is Nothing
Counterpart of isJust. You can use this with if statement.
- valueOr(this: Maybe, def: T): T
If this is Just, this function returns the inner value of this.
If not, this returns def (default value) you passed.
- valueOrThrow(this: Maybe, err: Error): T
If this is Just, this function returns the inner value of this.
If not, this throws err you passed.
- valueOrCompute(this: Maybe, f: Fun<[], T>): T
If this is Just, this function returns the inner value of this.
If not, this invoke f with inner value of current this, and return the result.

$3

- [Monad][monad-github]
- bind(this: Maybe, f: Fun<[T], Maybe>): Maybe
If this is Just, applies f to its inner value and return the result.
If this is Nothing, returns this.
- [Applicative][applicative-github]
- unit(v: U): Maybe
Return Just of v.
- ap(this: Maybe, f: Maybe>): Maybe
If this is Just and f is Just, applies the inner value of f to the inner value of this and returns Just of the result.
If this is Just but f is Nothing, returns f.
If this is Nothing, returns this.
- [Functor][functor-github]
- map(this: Maybe, f: Fun<[R], U>): Maybe
If this is Just, applies f to the inner value of this and returns Just of the result.
If this is Nothing, returns this.
- [Matchable][matchable-github]
- matchWith(this: Maybe, cases: MaybePatterns): U
If this is Just, applies cases.just to the inner value of this and returns the result.
If this is Nothing, invoke cases.nothing and returns the result.
- [Setoid][setoid-github]
- equals(other: Maybe): boolean
If this equals to other, return true.
If this does not equal to other, return false.
When both this and other are Justs and have complex inner values (object), this function tries equals method of inner value of this. In other words, this.equals(other) === this.value.equals(other.value)
- notEquals(other: Maybe): boolean
Returns true if and only if this.equals(other) returns false.



$3

You can use these functions like Maybe., for example, in case of map, you can access it with Maybe.map.

- unit(value: T): Maybe
Returns Just of value.
- of
Alias of unit
- from(value?: null): Nothing
- from(value: T): Just
Returns Nothing for value that is null or undefined, and returns Just of value for other values.
- maybe
Alias of from
- sequenceObject(obj: { [K in keyof O]: Maybe }): Maybe
Takes an obj of Maybes and returns an Maybe of object.
If for all keys of obj, correspoding values are Just, then this will return a Just of object whose keys are original keys and correspoding values are inner value of original values (Justs).
If for one or more keys of obj, values are Nothing, then this will return Nothing.
- sequenceArray(array: Maybe[]): Maybe
Takes an array of Maybes and returns an Maybe of array.
If all entries of array are Just, this will return a Just of array whose entries are inner values of original entries. Corresponding entries will have same indices.
If one or more entries of array are Nothing, this will return a Nothing.
- map(f: Fun<[T], U>): Fun<[Maybe], Maybe>
Returns a function that takes Maybe and maps its inner value using f.
map(f)(a) is same with a.map(f)`.

[lerna-badge]: https://img.shields.io/badge/maintained%20with-lerna-cc00ff.svg
[lerna]: https://lernajs.io/

[prs-welcome-badge]: https://img.shields.io/badge/PRs-welcome-brightgreen.svg
[prs-welcome]: http://makeapullrequest.com

[repo-supported-typescript-badge]: https://img.shields.io/badge/support-typescript%40%3E%3D3.0-007acc.svg
[supported-typescript]: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-0.html

[repo-slack-badge]: https://typed-f.now.sh/slack/badge.svg?style=for-the-badge&logo=slack
[repo-slack]: https://typed-f.now.sh/slack/welcome

[repo-circleci]: https://circleci.com/gh/Ailrun/typed-f/tree/master
[repo-circleci-badge]: https://img.shields.io/circleci/project/github/Ailrun/typed-f/master.svg?logo=circleci

[repo-github]: https://github.com/Ailrun/typed-f
[repo-github-releases]: https://github.com/Ailrun/typed-f/releases
[repo-github-watch]: https://github.com/Ailrun/typed-f/watchers
[repo-github-star]: https://github.com/Ailrun/typed-f/stargazers

[repo-github-license-badge]: https://img.shields.io/github/license/Ailrun/typed-f.svg
[repo-github-tag-badge]: https://img.shields.io/github/tag/Ailrun/typed-f.svg?colorB=blue
[repo-github-watch-badge]: https://img.shields.io/github/watchers/Ailrun/typed-f.svg?style=social
[repo-github-star-badge]: https://img.shields.io/github/stars/Ailrun/typed-f.svg?style=social

[applicative-github]: https://github.com/Ailrun/typed-f/tree/master/packages/applicative
[either-github]: https://github.com/Ailrun/typed-f/tree/master/packages/either
[function-github]: https://github.com/Ailrun/typed-f/tree/master/packages/function
[functor-github]: https://github.com/Ailrun/typed-f/tree/master/packages/functor
[lens-github]: https://github.com/Ailrun/typed-f/tree/master/packages/lens
[matchable-github]: https://github.com/Ailrun/typed-f/tree/master/packages/matchable
[maybe-github]: https://github.com/Ailrun/typed-f/tree/master/packages/maybe
[monad-github]: https://github.com/Ailrun/typed-f/tree/master/packages/monad
[setoid-github]: https://github.com/Ailrun/typed-f/tree/master/packages/setoid
[tagged-github]: https://github.com/Ailrun/typed-f/tree/master/packages/tagged

[applicative-npm]: https://www.npmjs.com/package/@typed-f/applicative
[either-npm]: https://www.npmjs.com/package/@typed-f/either
[function-npm]: https://www.npmjs.com/package/@typed-f/function
[functor-npm]: https://www.npmjs.com/package/@typed-f/functor
[lens-npm]: https://www.npmjs.com/package/@typed-f/lens
[matchable-npm]: https://www.npmjs.com/package/@typed-f/matchable
[maybe-npm]: https://www.npmjs.com/package/@typed-f/maybe
[monad-npm]: https://www.npmjs.com/package/@typed-f/monad
[setoid-npm]: https://www.npmjs.com/package/@typed-f/setoid
[tagged-npm]: https://www.npmjs.com/package/@typed-f/tagged

[applicative-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Fapplicative%2Fpackage.json
[either-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Feither%2Fpackage.json
[function-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Ffunction%2Fpackage.json
[functor-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Ffunctor%2Fpackage.json
[lens-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Flens%2Fpackage.json
[matchable-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Fmatchable%2Fpackage.json
[maybe-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Fmaybe%2Fpackage.json
[monad-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Fmonad%2Fpackage.json
[setoid-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Fsetoid%2Fpackage.json
[tagged-snyk-badge]: https://snyk.io/test/github/Ailrun/typed-f/badge.svg?targetFile=packages%2Ftagged%2Fpackage.json

[applicative-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/applicative/latest.svg?logo=npm&label=latest&colorB=blue
[either-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/either/latest.svg?logo=npm&label=latest&colorB=blue
[function-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/function/latest.svg?logo=npm&label=latest&colorB=blue
[functor-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/functor/latest.svg?logo=npm&label=latest&colorB=blue
[lens-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/lens/latest.svg?logo=npm&label=latest&colorB=blue
[matchable-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/matchable/latest.svg?logo=npm&label=latest&colorB=blue
[maybe-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/maybe/latest.svg?logo=npm&label=latest&colorB=blue
[monad-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/monad/latest.svg?logo=npm&label=latest&colorB=blue
[setoid-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/setoid/latest.svg?logo=npm&label=latest&colorB=blue
[tagged-npm-version-badge]: https://img.shields.io/npm/v/@typed-f/tagged/latest.svg?logo=npm&label=latest&colorB=blue

[applicative-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[either-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[function-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[functor-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[lens-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[matchable-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[maybe-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[monad-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[setoid-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json
[tagged-snyk]: https://snyk.io/test/github/Ailrun/typed-f?targetFile=packages%2Flens%2Fpackage.json