pull-monad

Monadic functions for pull-streams

These are the methods that make something "monadic." These functions and their interactions with each other satisfy the laws laid out in fantasy-land.

Usually these methods exist on the protytpe and are used like so:

const lift2 = (f, a, b) => b.ap(a.map(f))

Because these are simply through's, though, they must be used as such:

const lift2 = (f, a, b) => pull(b, ap(pull(a, map(f))))

example

const pull = require('pull-stream')
const { map, of, ap, chain } = require('pull-monad')
 
const plus1 = x => x + 1                       // takes a number and returns a number
const times7 = x => x * 7                      // takes a number and returns a number
const triplicate = x => pull.values([x, x, x]) // takes a number and returns a stream
 
pull(
  lift2(a => b => a + b, of(1), of(2)),
  map(times7),
  chain(triplicate),
  ap(of(plus1)),
  pull.collect((err, arr) => console.log(arr)))
 
// => [22, 22, 22]