js/env.js

   1 // Node vs browser behavior
   2 var env = {};
   3 if (typeof module === 'undefined') {
   4     var exports = env;
   5 }
   6
   7 // Env implementation
   8 function Env(outer, binds, exprs) {
   9     this.data = {};
  10     this.outer = outer || null;
  11
  12     if (binds && exprs) {
  13         // Returns a new Env with symbols in binds bound to
  14         // corresponding values in exprs
  15         // TODO: check types of binds and exprs and compare lengths
  16         for (var i=0; i<binds.length;i++) {
  17             if (binds[i].value === "&") {
  18                 // variable length arguments
  19                 this.data[binds[i+1].value] = Array.prototype.slice.call(exprs, i);
  20                 break;
  21             } else {
  22                 this.data[binds[i].value] = exprs[i];
  23             }
  24         }
  25     }
  26     return this;
  27 }
  28 Env.prototype.find = function (key) {
  29     if (!key.constructor || key.constructor.name !== 'Symbol') {
  30         throw new Error("env.find key must be a symbol")
  31     }
  32     if (key.value in this.data) { return this; }
  33     else if (this.outer) {  return this.outer.find(key); }
  34     else { return null; }
  35 };
  36 Env.prototype.set = function(key, value) {
  37     if (!key.constructor || key.constructor.name !== 'Symbol') {
  38         throw new Error("env.set key must be a symbol")
  39     }
  40     this.data[key.value] = value;
  41     return value;
  42 };
  43 Env.prototype.get = function(key) {
  44     if (!key.constructor || key.constructor.name !== 'Symbol') {
  45         throw new Error("env.get key must be a symbol")
  46     }
  47     var env = this.find(key);
  48     if (!env) { throw new Error("'" + key.value + "' not found"); }
  49     return env.data[key.value];
  50 };
  51
  52 exports.Env = env.Env = Env;