fixed-point.js

var Bacon = require("baconjs");
var _ = require("lodash");

// :: number -> number
var f = function (x) { return Math.cos(x); };

// :: number
var threshold = 1e-5;

// :: number -> number
var round = function (x) { return Math.round(x * 1e4) * 1e-4; };

// :: Bus number
var input = new Bacon.Bus();

// :: EventSource { curr : number, next : number, cond : bool }
var tmp = input.map(function (x) {
  var next = f(x);
  return { curr: x, next: next, cond: Math.abs(x - next) < threshold };
});

// :: Property number
var out = tmp.filter(".cond").map(".next").map(round).skipDuplicates().toProperty();

// :: EventSource number
var feedback = tmp.filter(function (p) {
  return !p.cond;
}).map(".next").delay(0);  // this delay is important!

input.plug(feedback);

out.log("out");
input.log("in ");

input.push(1);
input.push(-1);
input.push(0.7);