WebPPL: Monty Hall (Solution 1: doesn't resort to any "without loss of generality" argument)

MontyHall_WebPPL_no-wlog.js

var MontyHall = function () {
  var car = randomInteger({n: 3})
  var our_choice = randomInteger({n: 3})
  var all_doors_but = function (d1, d2) {
    return filter(function(d){return d != d1 & d != d2 }, [0,1,2])
  }
  var monty = categorical({vs: all_doors_but(car, our_choice)})
  var door_not_opened = all_doors_but(monty, our_choice)[0]

  return car == door_not_opened ? "change wins": "keep wins"
}

viz(Infer(MontyHall))