function Pos(x,y) { this.x = x; this.y = y; this.toString = function() { return x+","+y; } this.sub = function(pos2) { return new Pos(this.x - pos2.x,this.y - pos2.y) } this.add = function(pos2) { return new Pos(this.x + pos2.x,this.y + pos2.y) } this.is_equal = function(pos2) { return Math.abs(pos2.x) == Math.abs(this.x) && Math.abs(pos2.y) == Math.abs(this.y); } }