egg_array.js

/*
 * The array function gets a different amount of arguments each time.
 * Since we can prospect the number of arguments the function is 
 * going to get, it expects none (function())
 * The "arguments" keyword is an object that is created with each function
 * and contains the list of arguments as an array-like object
 */
topEnv["array"] = function() {
  return Array.prototype.slice.call(arguments, 0);
};

topEnv["length"] = function(arr) {
  return arr.length;
};

topEnv["element"] = function(arr, i) {
  return arr[i];
};

run("do(define(sum, fun(array,",
    "     do(define(i, 0),",
    "        define(sum, 0),",
    "        while(<(i, length(array)),",
    "          do(define(sum, +(sum, element(array, i))),",
    "             define(i, +(i, 1)))),",
    "        sum))),",
    "   print(sum(array(1, 2, 3))))");
// → 6