function HashSet() {
    var _hash=new Array();
    var _keys=new Array();
    var _count=0;
    
	this.keys = function() {
	        var ret=new Array();
	        var l=_count;
	        for(var i=0;i<l;++i) {
	            ret.push(_keys[i]);
	        }
	        return ret;
    }
	    
	this.values = function() {
	        var ret=new Array();
	        var l=_count;
	        for(var i=0;i<l;++i) {
	            var k=_keys[i];
	            ret.push(_hash[_keys[i]]);
	        }
	        return ret;
	}
	
	this.add = function(key,value) {
	        if(typeof(_hash[key])=='undefined') {
	            _keys.push(key);
	            _count++;
	        }
	        _hash[key]=value;        
	}
	    
	this.getItem = function(key) {
	        return _hash[key];
	}
	
	this.setItem = function(key,value) {
	        _hash[key]=value;
	}
	    
	this.exists = function(key) {
	        return typeof(_hash[key])!='undefined';
	}
	    
	this.removeAll = function() {
	        _hash=new Array();
	        _keys=new Array();
	        _count=0;
	}
	
	this.count = function() {
	        return _count;
	}
	    
	    // very slow for now
	this.remove = function(key) {
	        var newHash=new Array();
	        var newKeys=new Array();
	        var l=_keys.length;
	        _count=0;
	        for(var i=0;i<l;++i) {
	            var ik=keys[i];
	            if(ik!=key) {
	                newKeys.push(ik);
	                newHash[ik]=_hash[ik];
	                _count++;
	            }
	        }
	        _hash=newHash;
	        _keys=newKeys;
	}
}