rsa_gradable_original.wppl

// This code is from http://gscontras.github.io/ESSLLI-2016/chapters/3-semantics.html

///fold:
var marginalize = function(dist, key){
  return Infer({method: "enumerate"}, function(){
    return sample(dist)[key];
  })
}
///

var book = {
  "prices": [2, 6, 10, 14, 18, 22, 26, 30],
  "probabilities": [1, 2, 3, 4, 4, 3, 2, 1]
};

var statePrior = function() {
  return categorical(book.probabilities, book.prices);
};

var thetaPrior = function() {
    return uniformDraw(book.prices);
};

var alpha = 1; // rationality parameter

var utterances = ["expensive", ""];
var cost = {
  "expensive": 1,
  "": 0
};
var utterancePrior = function() {
  var uttProbs = map(function(u) {return Math.exp(-cost[u]) }, utterances);
  return categorical(uttProbs, utterances);
};

var meaning = function(utterance, price, theta) {
  if (utterance == "expensive") {
    return price >= theta;
  } else {
    return true;
  }
};

var literalListener = cache(function(utterance, theta, item) {
  return Infer({method: "enumerate"}, function() {
    var price = statePrior();

    condition(meaning(utterance, price, theta))

    return price;
  });
});

var speaker = cache(function(price, theta, item) {
  return Infer({method: "enumerate"}, function() {
    var utterance = utterancePrior();

    factor( alpha * literalListener(utterance, theta, item).score(price) );

    return utterance;
  });
});

var pragmaticListener = function(utterance, item) {
  return Infer({method: "enumerate"}, function() {
    var price = statePrior();
    var theta = thetaPrior();
    factor(speaker(price, theta, item).score(utterance));
    return { price: price, theta: theta };
  });
};

var expensiveBook = pragmaticListener("expensive", "book");
viz.auto(marginalize(expensiveBook, "price"));
viz.auto(marginalize(expensiveBook, "theta"));