vector2D.js

define([], function(){
	//This is a subset of vector3D.js
	//see vector3D.js for information about each function
	
	function Vector2D(a, b){
		this.vectorArray = new Float32Array(2);
		this.vectorArray[0] = a;
		this.vectorArray[1] = b;
	}
	
	Vector2D.prototype.getVectorAsArray = function(){
		return this.vectorArray;	
	};
	
	Vector2D.prototype.set = function(a, b){ //Completely overrides current this.vectorArray
		this.vectorArray = new Float32Array(2);
		this.vectorArray[0] = a;
		this.vectorArray[1] = b;
	};
	
	Vector2D.prototype.setAt = function(i, a){
		this.vectorArray[i] = a;
	};
	
	Vector2D.prototype.at = function(i){
		return this.vectorArray[i];
	};
	
	Vector2D.prototype.getLength = function(){
		return 2;
	};
	
	Vector2D.prototype.dot = function(v){
		var a = this.vectorArray;
		var b = v.vectorArray;
		var result = a[0] * b[0] + a[1] * b[1];
	
		return result;
	};
		
	Vector2D.prototype.magnitude = function(){
		var a = this.vectorArray;
		var k = a[0] * a[0] + a[1] * a[1];
		return Math.sqrt(k);
	};
	
	Vector2D.prototype.add = function(v){
		var a = this.vectorArray;
		var b = v.vectorArray;
		var result = new Vector2D(a[0] + b[0], a[1] + b[1]);
		return result;
	};
		
	Vector2D.prototype.subtract = function(v){
		var a = this.vectorArray;
		var b = v.vectorArray;
		var result = new Vector2D(a[0] - b[0], a[1] - b[1]);
		return result;
	};
	
	Vector2D.prototype.multiply = function(x){ //scalar multiplication
		var a = this.vectorArray;
		var result = new Vector2D(a[0] * x, a[1] * x);
		return result;
	};
	
	Vector2D.prototype.unit = function(){
		if (typeof this.unitVector === "undefined") {
			this.unitVector = this.multiply(1 / this.magnitude());
		}
		return this.unitVector;
	};
	
	Vector2D.prototype.angle = function(v){ //angle between two vectors
		var angle = Math.acos(this.dot(v) / (this.magnitude() * v.magnitude()));
		return angle;
	};
	
	Vector2D.prototype.area = function(v){ //area of the parallelogram formed by two vectors
		
		var a = this.vectorArray[0] * v.vectorArray[1] - this.vectorArray[1] * v.vectorArray[0];
		return a;
	};
	return Vector2D;
});