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// Copyright 2007 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview Defines a 2-element vector class that can be used for
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 * coordinate math, useful for animation systems and point manipulation.
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 *
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 * Vec2 objects inherit from goog.math.Coordinate and may be used wherever a
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 * Coordinate is required. Where appropriate, Vec2 functions accept both Vec2
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 * and Coordinate objects as input.
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 *
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 * @author [email protected] (Shawn Brenneman)
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 */
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goog.provide('goog.math.Vec2');
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goog.require('goog.math');
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goog.require('goog.math.Coordinate');
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/**
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 * Class for a two-dimensional vector object and assorted functions useful for
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 * manipulating points.
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 *
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 * @param {number} x The x coordinate for the vector.
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 * @param {number} y The y coordinate for the vector.
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 * @struct
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 * @constructor
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 * @extends {goog.math.Coordinate}
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 */
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goog.math.Vec2 = function(x, y) {
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  /**
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   * X-value
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   * @type {number}
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   */
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  this.x = x;
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  /**
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   * Y-value
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   * @type {number}
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   */
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  this.y = y;
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};
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goog.inherits(goog.math.Vec2, goog.math.Coordinate);
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/**
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 * @return {!goog.math.Vec2} A random unit-length vector.
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 */
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goog.math.Vec2.randomUnit = function() {
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  var angle = Math.random() * Math.PI * 2;
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  return new goog.math.Vec2(Math.cos(angle), Math.sin(angle));
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};
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/**
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 * @return {!goog.math.Vec2} A random vector inside the unit-disc.
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 */
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goog.math.Vec2.random = function() {
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  var mag = Math.sqrt(Math.random());
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  var angle = Math.random() * Math.PI * 2;
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  return new goog.math.Vec2(Math.cos(angle) * mag, Math.sin(angle) * mag);
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};
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/**
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 * Returns a new Vec2 object from a given coordinate.
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 * @param {!goog.math.Coordinate} a The coordinate.
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 * @return {!goog.math.Vec2} A new vector object.
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 */
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goog.math.Vec2.fromCoordinate = function(a) {
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  return new goog.math.Vec2(a.x, a.y);
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};
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/**
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 * @return {!goog.math.Vec2} A new vector with the same coordinates as this one.
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 * @override
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 */
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goog.math.Vec2.prototype.clone = function() {
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  return new goog.math.Vec2(this.x, this.y);
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};
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/**
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 * Returns the magnitude of the vector measured from the origin.
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 * @return {number} The length of the vector.
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 */
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goog.math.Vec2.prototype.magnitude = function() {
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  return Math.sqrt(this.x * this.x + this.y * this.y);
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};
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/**
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 * Returns the squared magnitude of the vector measured from the origin.
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 * NOTE(brenneman): Leaving out the square root is not a significant
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 * optimization in JavaScript.
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 * @return {number} The length of the vector, squared.
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 */
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goog.math.Vec2.prototype.squaredMagnitude = function() {
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  return this.x * this.x + this.y * this.y;
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};
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/**
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 * @return {!goog.math.Vec2} This coordinate after scaling.
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 * @override
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 */
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goog.math.Vec2.prototype.scale =
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    /** @type {function(number, number=):!goog.math.Vec2} */
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    (goog.math.Coordinate.prototype.scale);
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/**
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 * Reverses the sign of the vector. Equivalent to scaling the vector by -1.
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 * @return {!goog.math.Vec2} The inverted vector.
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 */
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goog.math.Vec2.prototype.invert = function() {
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  this.x = -this.x;
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  this.y = -this.y;
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  return this;
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};
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/**
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 * Normalizes the current vector to have a magnitude of 1.
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 * @return {!goog.math.Vec2} The normalized vector.
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 */
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goog.math.Vec2.prototype.normalize = function() {
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  return this.scale(1 / this.magnitude());
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};
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/**
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 * Adds another vector to this vector in-place.
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 * @param {!goog.math.Coordinate} b The vector to add.
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 * @return {!goog.math.Vec2}  This vector with {@code b} added.
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 */
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goog.math.Vec2.prototype.add = function(b) {
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  this.x += b.x;
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  this.y += b.y;
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  return this;
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};
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/**
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 * Subtracts another vector from this vector in-place.
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 * @param {!goog.math.Coordinate} b The vector to subtract.
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 * @return {!goog.math.Vec2} This vector with {@code b} subtracted.
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 */
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goog.math.Vec2.prototype.subtract = function(b) {
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  this.x -= b.x;
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  this.y -= b.y;
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  return this;
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};
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/**
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 * Rotates this vector in-place by a given angle, specified in radians.
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 * @param {number} angle The angle, in radians.
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 * @return {!goog.math.Vec2} This vector rotated {@code angle} radians.
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 */
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goog.math.Vec2.prototype.rotate = function(angle) {
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  var cos = Math.cos(angle);
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  var sin = Math.sin(angle);
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  var newX = this.x * cos - this.y * sin;
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  var newY = this.y * cos + this.x * sin;
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  this.x = newX;
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  this.y = newY;
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  return this;
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};
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/**
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 * Rotates a vector by a given angle, specified in radians, relative to a given
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 * axis rotation point. The returned vector is a newly created instance - no
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 * in-place changes are done.
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 * @param {!goog.math.Vec2} v A vector.
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 * @param {!goog.math.Vec2} axisPoint The rotation axis point.
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 * @param {number} angle The angle, in radians.
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 * @return {!goog.math.Vec2} The rotated vector in a newly created instance.
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 */
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goog.math.Vec2.rotateAroundPoint = function(v, axisPoint, angle) {
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  var res = v.clone();
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  return res.subtract(axisPoint).rotate(angle).add(axisPoint);
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};
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/** @override */
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goog.math.Vec2.prototype.equals = function(b) {
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  if (this == b) {
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    return true;
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  }
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  return b instanceof goog.math.Vec2 && !!b && this.x == b.x && this.y == b.y;
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};
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/**
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 * Returns the distance between two vectors.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {number} The distance.
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 */
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goog.math.Vec2.distance = goog.math.Coordinate.distance;
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/**
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 * Returns the squared distance between two vectors.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {number} The squared distance.
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 */
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goog.math.Vec2.squaredDistance = goog.math.Coordinate.squaredDistance;
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/**
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 * Compares vectors for equality.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {boolean} Whether the vectors have the same x and y coordinates.
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 */
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goog.math.Vec2.equals = goog.math.Coordinate.equals;
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/**
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 * Returns the sum of two vectors as a new Vec2.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {!goog.math.Vec2} The sum vector.
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 */
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goog.math.Vec2.sum = function(a, b) {
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  return new goog.math.Vec2(a.x + b.x, a.y + b.y);
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};
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/**
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 * Returns the difference between two vectors as a new Vec2.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {!goog.math.Vec2} The difference vector.
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 */
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goog.math.Vec2.difference = function(a, b) {
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  return new goog.math.Vec2(a.x - b.x, a.y - b.y);
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};
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/**
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 * Returns the dot-product of two vectors.
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 * @param {!goog.math.Coordinate} a The first vector.
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 * @param {!goog.math.Coordinate} b The second vector.
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 * @return {number} The dot-product of the two vectors.
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 */
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goog.math.Vec2.dot = function(a, b) {
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  return a.x * b.x + a.y * b.y;
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};
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/**
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 * Returns the determinant of two vectors.
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 * @param {!goog.math.Vec2} a The first vector.
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 * @param {!goog.math.Vec2} b The second vector.
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 * @return {number} The determinant of the two vectors.
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 */
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goog.math.Vec2.determinant = function(a, b) {
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  return a.x * b.y - a.y * b.x;
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};
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/**
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 * Returns a new Vec2 that is the linear interpolant between vectors a and b at
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 * scale-value x.
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 * @param {!goog.math.Coordinate} a Vector a.
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 * @param {!goog.math.Coordinate} b Vector b.
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 * @param {number} x The proportion between a and b.
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 * @return {!goog.math.Vec2} The interpolated vector.
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 */
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goog.math.Vec2.lerp = function(a, b, x) {
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  return new goog.math.Vec2(
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      goog.math.lerp(a.x, b.x, x), goog.math.lerp(a.y, b.y, x));
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};
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