lab11: init

lab11/functional.js

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+var foldl = function (f, acc, array) {
+}
+
+console.log(foldl(function(x,y){return x+y}, 0, [1,2,3]));
+
+var foldr = function (f, z, array) {
+}
+
+console.log(foldl(function(x,y){return x/y}, 1, [2,4,8]));
+
+var map = function (f, array) {
+}
+
+console.log(map(function(x){return x+x}, [1,2,3,5,7,9,11,13]));
+
+
+// Write a curry function as we discussed in class.
+// Create a `double` method using the curry function
+// and the following `mult` function.
+function mult(x,y) {
+  return x * y;
+}
+

lab11/intro.js

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+// Highlights some of the basic functionality of JavaScript.
+
+// With JavaScript, we can specify new values with the var keyword.
+// Using the keyword var is not strictly required, but it is considered a best practice.
+var x=42, y=7;
+
+
+// JavaScript is a functional language, in the sense that functions are first class objects.
+// (WARNING: not everyone likes this definition of functional languages).
+// We can write them in two different ways.
+function add(a,b) {
+  return a + b;
+}
+
+var square = function(a) {
+  return a * a;
+}
+
+// Printing varies by platform. Node uses console.log.
+console.log("x + y = " + add(x,y));
+
+// That is annoying, so let's store it in another variable.
+var print = console.log;
+
+print("x^2 = " + square(x));
+
+// Since functions are first class values, we can do interesting stuff with them.
+function applyFunToX(f) {
+  f(x);
+}
+
+applyFunToX(print);
+
+// JavaScript functions are **closures**.  They remember their surrounding scope.
+var getNextInt = function() {
+  var nextInt = 0;
+  return function() {
+    return nextInt++;
+  }
+}();
+
+print(getNextInt());
+print(getNextInt());
+print(getNextInt());
+
+
+// Objects in JavaScript work a little differently.
+var complex = { real: 3, imaginary: 1 };
+print (complex);
+
+var Dog = {
+  speak: function() { print('bark!'); }
+};
+
+rex = { name: 'rex', __proto__: Dog } // Manually setting the prototype chain -- not universal
+rex.speak();
+
+// We can add or remove properties at runtime
+rex['favoriteToy'] = 'squeaky ball'; // could write this as rex.favoriteToy
+print(rex);
+//delete rex.name;
+
+// We can override properties if we wish
+rex.speak = function() { print('grr....'); }
+rex.speak();
+
+// Or delete them, with perhaps surprising results
+delete rex.speak;
+rex.speak();
+
+
+// The more standard way of adding JavaScript objects: first create a constructor
+function Cat(name, breed) {
+  this.name = name;
+  this.breed = breed;
+  this.speak = function() { print('meow!'); }
+}
+
+var garfield = new Cat('Garfield', 'Orange tabby');
+print(garfield);
+garfield.speak();
+
+Cat.prototype.makeAngryNoise = function() {
+  print('hiss');
+}
+garfield.makeAngryNoise();
+
+Cat.prototype.sayName = function() {
+  print("My name is " + this.name);
+}
+garfield.sayName();
+
+garfield.favoriteFood = 'lasagna';
+
+var animals = [garfield, new Cat('mimi', 'Calico'), rex];
+
+var forEach = function(arr,f) {
+  var i;
+  for (i=0; i<arr.length; i++) {
+    f(arr[i]);
+  }
+}
+print("Displaying all animals");
+forEach(animals, print);
+
+print("Each animal say your name");
+forEach(animals, function(animal) {
+  animal.speak();
+  //animal.sayName(); // Won't work -- rex has no sayName method
+  Cat.prototype.sayName.apply(animal);
+});
+
+
+Function.prototype.curry = function() {
+  var slice = Array.prototype.slice,
+      args = slice.apply(arguments),
+      that = this;
+  return function () {
+    return that.apply(null, args.concat(slice.apply(arguments)));
+  };
+};
+
+var addOne = add.curry(1);
+console.log(addOne(3));
+