Applicative wrapper

readme.md

Make native Set<T> applicative via wrapper

index.js

//@flow

import {interpret} from './wrap'

const foo = () => interpret(new Set([0, 1, 2]))
  .map(x => x + 1)
  .ap( interpret(new Set([x => x * 10])) )

wrap.js

//@flow

export const interpret = <A>(set: Set<A>) => ({
  of(value: A) {
    return interpret(new Set([value]))
  },
  empty(){ return interpret(new Set()) },
  map<B>(fn: A => B) {
    return interpret(
      new Set(map(fn, set))
    )
  },
  ap<B>(fnSet: Set<(_: A) => B>) {
    return interpret(
      new Set([...fnSet].reduce(
        (acc, fn) => [...acc, ...map(fn, set)],
        []
      ))
    )
  }
})

function map<A, B>(fn: A => B, set: Set<A>): B[] {
  return [...set].map(fn)
}