crocks/logic/implies.js

A collection of well known Algebraic Datatypes for your utter enjoyment.

/** @license ISC License (c) copyright 2018 original and current authors */
/** @author Ian Hofmann-Hicks (evil) */

var curry = require('../core/curry')
var isPredOrFunc = require('../core/isPredOrFunc')
var predOrFunc = require('../core/predOrFunc')

// implies :: (a -> Boolean) | Pred -> (a -> Boolean) -> a -> Boolean
function implies(p, q) {
  if(!(isPredOrFunc(p) && isPredOrFunc(q))) {
    throw new TypeError(
      'implies: Preds or predicate functions required for first two arguments'
    )
  }

  return function (x) { return !predOrFunc(p, x) || !!predOrFunc(q, x); }
}

module.exports = curry(implies)