var worldPrior = function() {
  var num_nice_people = randomInteger(4) //3 people.. 0-3 can be nice.
  return num_nice_people
}

var utterancePrior = function() {
  var utterances = ['some of the people are nice',
                    'all of the people are nice',
                    'none of the people are nice']
  var i = randomInteger(utterances.length)
  return utterances[i]
}

var meaning = function(utt, world) {
  return utt == 'some of the people are nice' ? world > 0 :
         utt == 'all of the people are nice' ? world == 3 :
         utt == 'none of the people are nice' ? world == 0 :
         true
}

var literalListener = cache(function(utterance) {
  Enumerate(function() {
    var world = worldPrior()
    var m = meaning(utterance, world)
    factor(m ? 0 : -Infinity)
    return world
  })
})

var speaker = cache(function(world) {
  Enumerate(function() {
    var utterance = utterancePrior()
    var L = literalListener(utterance)
    factor(L.score([], world))
    return utterance
  })
})

var listener = function(utterance) {
  Enumerate(function() {
    var world = worldPrior()
    var S = speaker(world)
    factor(S.score([], utterance))
    return world
  })
}

listener('some of the people are nice')