// set data type for javascript

/*
Function.prototype.invert = function(){
	var self = this;
	return function(){
		return !self.apply(this,arguments)
	}
};*/

function Set(a){
	if(a.isSet) return a;
	var self;
	var index = {};
	self = [];
	self.isSet = true;
	self.add = function(v){
		if(self._has(v)) return;
		self.push(v);
		index[(typeof v) + "_" + v] = true;
		return self;
	};
	self._has = function(v){
		return index.hasOwnProperty((typeof v)+"_"+v)
	};
	var can_set = function(v){
		var t = typeof v;
		return (t == "string" || t == "boolean" || t == "number");
	};
	var invert = function(f){
		return function(){
			return !f.apply(this,arguments)
		}
	}
	a.filter(can_set).forEach(self.add);
	
	// s <= t
	self.issubset = function(t){return self.every(t._has)};
	// s >= t
	self.issuperset = function(t){return t.every(self._has)};
	// s | t
	self.union = function(t){return new Set(self.concat(t))};
	// s & t
	self.intersection = function(t){return new Set(self.filter(t._has))};
	// s - t
	self.difference = function(t){return new Set(self.filter(invert(t._has)))};
	// s ^ t
	self.symmetric_difference = function(t){
		//return new Set(self.union(t).difference(self.intersection(t)));
		return new Set(self.concat(t).filter(function(v){return (!self._has(v) || !t._has(v))}));
	};
	// convert array to set object
	var conv = function(f){
		return function(t){
			t = new Set(t);
			return f(t)
		}
	};
	var methods = "issubset,issuperset,union,intersection,difference,symmetric_difference".split(",");
	methods.forEach(function(v){
		self[v] = conv(self[v])
	});

	self.copy = function(){
		return new Set(self.concat())
	};
	self.update = function(t){
		t.forEach(self.add);
		return self;
	};
	self.intersection_update = function(t){
		self.clear();
		self.update(self.intersection(t))
		return self;
	};
	self.difference_update = function(t){
		self.clear();
		self.update(self.difference());
		return self;
	}
	self.symmetric_difference_update = function(){
		self.clear();
		self.update(self.symmetric_difference());
		return self;
	}
	self.discard = function(v){
		var pos = self.indexOf(v);
		if(pos != -1){
			return self.splice(pos,1)
		}
	}
	self.remove = self.discard;
	self.clear = function(){
		self.length = 0;
		index = {};
		return self;
	};
	return self;
}
function set(a){
	return new Set(a)
}