contravariant

Contravariant functors in JavaScript with Flow.

Mainly inspired by haskell contravariant.

See src/index.js and test/index.test.js.

Installation

$ npm install contravariant

API

interface IContravariant<-A>

• contramap<B>(fn: B => A): IContravariant<B>

class Predicate<-A>

• constructor(f: A => boolean)
• getPredicate(): A => boolean
• contramap<B>(fn: B => A): Predicate<B>

class Comparison<-A>

• constructor(f: (A, A) => number)
• getComparison(): (A, A) => number
• contramap<B>(fn: B => A): Comparison<B>

function defaultComparison(): Comparison<number>

class Equivalence<-A>

• constructor(f: (A, A) => boolean)
• getEquivalence(): (A, A) => boolean
• contramap<B>(fn: B => A): Equivalence<B>

function defaultEquivalence<A>(): Equivalence<A>

class Op<+A, -B>

• constructor(f: B => A)
• getOp(): B => A
• contramap<BB>(fn: BB => B): Op<A, BB>

Profunctors

interface IProfunctor<-B, +C>

• promap<A, D>(fn1: A => B, fn2: C => D): IProfunctor<A, D>

class Arrow<-B, +C>

• constructor(f: B => C)
• getArrow(): B => C
• promap<A, D>(fn1: A => B, fn2: C => D): Arrow<A, D>
• lmap<A>(fn1: A => B): Arrow<A, C>
• rmap<D>(fn2: C => D): Arrow<B, D>

See also

• https://hackage.haskell.org/package/contravariant-1.5/docs/Data-Functor-Contravariant.html
• https://github.com/fantasyland/fantasy-land#contravariant
• https://gist.github.com/Bannerets/07a71802e3468d252924091a65ac2b3c
• https://www.schoolofhaskell.com/school/to-infinity-and-beyond/pick-of-the-week/profunctors
• https://hackage.haskell.org/package/profunctors-5.3/docs/Data-Profunctor.html
• https://github.com/fantasyland/fantasy-land#profunctor