symtab.js

/*******************************************************************************
 * Copyright (c) 2013 Max Schaefer.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Max Schaefer - initial API and implementation
 *******************************************************************************/

/* Simple implementation of symbol tables. Uses
 * prototypal inheritance to model scoping. */
if(typeof define !== 'function') {
  var define = require('amdefine')(module);
}

define(function(require, exports) {
  function mangle(name) {
    return '$' + name;
  }

  function isMangled(name) {
    return name && name[0] === '$';
  }
  
  function Symtab(outer) {
    var self = Object.create(outer || Symtab.prototype);
    // every scope has a pointer to its outer scope, which may be null
    self.outer = outer;
    return self;
  }
  
  Symtab.prototype.get = function(name, deflt) {
    var mangled = mangle(name);
    if(!deflt || this.has(name))
      return this[mangled];
    this[mangled] = deflt;
    return deflt;
  };
  
  Symtab.prototype.has = function(name) {
    return mangle(name) in this;
  };

  Symtab.prototype.hasOwn = function(name) {
    return this.hasOwnProperty(mangle(name));
  };
  
  Symtab.prototype.set = function(name, value) {
    return this[mangle(name)] = value;
  };

  Symtab.prototype.values = function() {
    var values = [];
    for(var p in this)
      if(isMangled(p))
        values[values.length] = this[p];
    return values;
  };
  
  exports.Symtab = Symtab;
  return exports;
});