pointfree-fantasy/instances/array.js

Point free wrappers for fantasy land js.

var curry = require('lodash.curry');

var _flatten = function(xs) {
  return xs.reduce(function(a,b){return a.concat(b);}, []);
};

var _fmap = function(f) {
  var xs = this;
  return xs.map(function(x) { return f(x); }); //avoid index
};

Object.defineProperty(Array.prototype, 'fmap',{
  value: _fmap,
  writable: true,
  configurable: true,
  enumerable: false
});

var _empty = function() { return []; };

Object.defineProperty(Array.prototype, 'empty',{
  value: _empty,
  writable: true,
  configurable: true,
  enumerable: false
});

var _chain = function(f) { return _flatten(this.fmap(f)); };

Object.defineProperty(Array.prototype, 'chain',{
  value: _chain,
  writable: true,
  configurable: true,
  enumerable: false
});

var _of = function(x) { return [x]; };

Object.defineProperty(Array.prototype, 'of',{
  value: _of,
  writable: true,
  configurable: true,
  enumerable: false
});

var _ap = function(a2) {
  var a1 = this;
  return _flatten(a1.map(function(f){
    return a2.map(function(a){ return f(a); })
  }));
};

Object.defineProperty(Array.prototype, 'ap',{
  value: _ap,
  writable: true,
  configurable: true,
  enumerable: false
});

var _traverse = function(f, point) {
  var cons_f = function(ys, x){
    return f(x).map(function(x){ return function(y){ return y.concat(x); } }).ap(ys);
  }
  return this.reduce(cons_f, point([]));
};

Object.defineProperty(Array.prototype, 'traverse',{
  value: _traverse,
  writable: true,
  configurable: true,
  enumerable: false
});