WebPPL: Monty Hall (Solution 2: without loss of generality, suppose that we originally pick the 1st door and Monty opens the 2nd one)

MontyHall_WebPPL_wlog.js

var MontyHall = function () {
  var car = randomInteger({n: 3})
  var our_choice = randomInteger({n: 3})
  var monty = categorical({vs: filter(
    function(d){return d != car & d != our_choice }, [0,1,2])})
  
  condition((our_choice == 0) & (monty == 1))
  return car == 2 ? "change wins": "keep wins"
}

viz(Infer(MontyHall))