# Source: vec4.js

    import * as glMatrix from "./common.js";

    /**
     * 4 Dimensional Vector
     * @module vec4
     */

    /**
     * Creates a new, empty vec4
     *
     * @returns {vec4} a new 4D vector
     */
    export function create() {
      let out = new glMatrix.ARRAY_TYPE(4);
      if(glMatrix.ARRAY_TYPE != Float32Array) {
        out[0] = 0;
        out[1] = 0;
        out[2] = 0;
        out[3] = 0;
      }
      return out;
    }

    /**
     * Creates a new vec4 initialized with values from an existing vector
     *
     * @param {vec4} a vector to clone
     * @returns {vec4} a new 4D vector
     */
    export function clone(a) {
      let out = new glMatrix.ARRAY_TYPE(4);
      out[0] = a[0];
      out[1] = a[1];
      out[2] = a[2];
      out[3] = a[3];
      return out;
    }

    /**
     * Creates a new vec4 initialized with the given values
     *
     * @param {Number} x X component
     * @param {Number} y Y component
     * @param {Number} z Z component
     * @param {Number} w W component
     * @returns {vec4} a new 4D vector
     */
    export function fromValues(x, y, z, w) {
      let out = new glMatrix.ARRAY_TYPE(4);
      out[0] = x;
      out[1] = y;
      out[2] = z;
      out[3] = w;
      return out;
    }

    /**
     * Copy the values from one vec4 to another
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the source vector
     * @returns {vec4} out
     */
    export function copy(out, a) {
      out[0] = a[0];
      out[1] = a[1];
      out[2] = a[2];
      out[3] = a[3];
      return out;
    }

    /**
     * Set the components of a vec4 to the given values
     *
     * @param {vec4} out the receiving vector
     * @param {Number} x X component
     * @param {Number} y Y component
     * @param {Number} z Z component
     * @param {Number} w W component
     * @returns {vec4} out
     */
    export function set(out, x, y, z, w) {
      out[0] = x;
      out[1] = y;
      out[2] = z;
      out[3] = w;
      return out;
    }

    /**
     * Adds two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function add(out, a, b) {
      out[0] = a[0] + b[0];
      out[1] = a[1] + b[1];
      out[2] = a[2] + b[2];
      out[3] = a[3] + b[3];
      return out;
    }

    /**
     * Subtracts vector b from vector a
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function subtract(out, a, b) {
      out[0] = a[0] - b[0];
      out[1] = a[1] - b[1];
      out[2] = a[2] - b[2];
      out[3] = a[3] - b[3];
      return out;
    }

    /**
     * Multiplies two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function multiply(out, a, b) {
      out[0] = a[0] * b[0];
      out[1] = a[1] * b[1];
      out[2] = a[2] * b[2];
      out[3] = a[3] * b[3];
      return out;
    }

    /**
     * Divides two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function divide(out, a, b) {
      out[0] = a[0] / b[0];
      out[1] = a[1] / b[1];
      out[2] = a[2] / b[2];
      out[3] = a[3] / b[3];
      return out;
    }

    /**
     * Math.ceil the components of a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to ceil
     * @returns {vec4} out
     */
    export function ceil(out, a) {
      out[0] = Math.ceil(a[0]);
      out[1] = Math.ceil(a[1]);
      out[2] = Math.ceil(a[2]);
      out[3] = Math.ceil(a[3]);
      return out;
    }

    /**
     * Math.floor the components of a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to floor
     * @returns {vec4} out
     */
    export function floor(out, a) {
      out[0] = Math.floor(a[0]);
      out[1] = Math.floor(a[1]);
      out[2] = Math.floor(a[2]);
      out[3] = Math.floor(a[3]);
      return out;
    }

    /**
     * Returns the minimum of two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function min(out, a, b) {
      out[0] = Math.min(a[0], b[0]);
      out[1] = Math.min(a[1], b[1]);
      out[2] = Math.min(a[2], b[2]);
      out[3] = Math.min(a[3], b[3]);
      return out;
    }

    /**
     * Returns the maximum of two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {vec4} out
     */
    export function max(out, a, b) {
      out[0] = Math.max(a[0], b[0]);
      out[1] = Math.max(a[1], b[1]);
      out[2] = Math.max(a[2], b[2]);
      out[3] = Math.max(a[3], b[3]);
      return out;
    }

    /**
     * Math.round the components of a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to round
     * @returns {vec4} out
     */
    export function round(out, a) {
      out[0] = Math.round(a[0]);
      out[1] = Math.round(a[1]);
      out[2] = Math.round(a[2]);
      out[3] = Math.round(a[3]);
      return out;
    }

    /**
     * Scales a vec4 by a scalar number
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the vector to scale
     * @param {Number} b amount to scale the vector by
     * @returns {vec4} out
     */
    export function scale(out, a, b) {
      out[0] = a[0] * b;
      out[1] = a[1] * b;
      out[2] = a[2] * b;
      out[3] = a[3] * b;
      return out;
    }

    /**
     * Adds two vec4's after scaling the second operand by a scalar value
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @param {Number} scale the amount to scale b by before adding
     * @returns {vec4} out
     */
    export function scaleAndAdd(out, a, b, scale) {
      out[0] = a[0] + (b[0] * scale);
      out[1] = a[1] + (b[1] * scale);
      out[2] = a[2] + (b[2] * scale);
      out[3] = a[3] + (b[3] * scale);
      return out;
    }

    /**
     * Calculates the euclidian distance between two vec4's
     *
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {Number} distance between a and b
     */
    export function distance(a, b) {
      let x = b[0] - a[0];
      let y = b[1] - a[1];
      let z = b[2] - a[2];
      let w = b[3] - a[3];
      return Math.sqrt(x*x + y*y + z*z + w*w);
    }

    /**
     * Calculates the squared euclidian distance between two vec4's
     *
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {Number} squared distance between a and b
     */
    export function squaredDistance(a, b) {
      let x = b[0] - a[0];
      let y = b[1] - a[1];
      let z = b[2] - a[2];
      let w = b[3] - a[3];
      return x*x + y*y + z*z + w*w;
    }

    /**
     * Calculates the length of a vec4
     *
     * @param {vec4} a vector to calculate length of
     * @returns {Number} length of a
     */
    export function length(a) {
      let x = a[0];
      let y = a[1];
      let z = a[2];
      let w = a[3];
      return Math.sqrt(x*x + y*y + z*z + w*w);
    }

    /**
     * Calculates the squared length of a vec4
     *
     * @param {vec4} a vector to calculate squared length of
     * @returns {Number} squared length of a
     */
    export function squaredLength(a) {
      let x = a[0];
      let y = a[1];
      let z = a[2];
      let w = a[3];
      return x*x + y*y + z*z + w*w;
    }

    /**
     * Negates the components of a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to negate
     * @returns {vec4} out
     */
    export function negate(out, a) {
      out[0] = -a[0];
      out[1] = -a[1];
      out[2] = -a[2];
      out[3] = -a[3];
      return out;
    }

    /**
     * Returns the inverse of the components of a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to invert
     * @returns {vec4} out
     */
    export function inverse(out, a) {
      out[0] = 1.0 / a[0];
      out[1] = 1.0 / a[1];
      out[2] = 1.0 / a[2];
      out[3] = 1.0 / a[3];
      return out;
    }

    /**
     * Normalize a vec4
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a vector to normalize
     * @returns {vec4} out
     */
    export function normalize(out, a) {
      let x = a[0];
      let y = a[1];
      let z = a[2];
      let w = a[3];
      let len = x*x + y*y + z*z + w*w;
      if (len > 0) {
        len = 1 / Math.sqrt(len);
        out[0] = x * len;
        out[1] = y * len;
        out[2] = z * len;
        out[3] = w * len;
      }
      return out;
    }

    /**
     * Calculates the dot product of two vec4's
     *
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @returns {Number} dot product of a and b
     */
    export function dot(a, b) {
      return a[0] * b[0] + a[1] * b[1] + a[2] * b[2] + a[3] * b[3];
    }

    /**
     * Performs a linear interpolation between two vec4's
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the first operand
     * @param {vec4} b the second operand
     * @param {Number} t interpolation amount, in the range [0-1], between the two inputs
     * @returns {vec4} out
     */
    export function lerp(out, a, b, t) {
      let ax = a[0];
      let ay = a[1];
      let az = a[2];
      let aw = a[3];
      out[0] = ax + t * (b[0] - ax);
      out[1] = ay + t * (b[1] - ay);
      out[2] = az + t * (b[2] - az);
      out[3] = aw + t * (b[3] - aw);
      return out;
    }

    /**
     * Generates a random vector with the given scale
     *
     * @param {vec4} out the receiving vector
     * @param {Number} [scale] Length of the resulting vector. If ommitted, a unit vector will be returned
     * @returns {vec4} out
     */
    export function random(out, scale) {
      scale = scale || 1.0;

      // Marsaglia, George. Choosing a Point from the Surface of a
      // Sphere. Ann. Math. Statist. 43 (1972), no. 2, 645--646.
      // http://projecteuclid.org/euclid.aoms/1177692644;
      var v1, v2, v3, v4;
      var s1, s2;
      do {
        v1 = glMatrix.RANDOM() * 2 - 1;
        v2 = glMatrix.RANDOM() * 2 - 1;
        s1 = v1 * v1 + v2 * v2;
      } while (s1 >= 1);
      do {
        v3 = glMatrix.RANDOM() * 2 - 1;
        v4 = glMatrix.RANDOM() * 2 - 1;
        s2 = v3 * v3 + v4 * v4;
      } while (s2 >= 1);

      var d = Math.sqrt((1 - s1) / s2);
      out[0] = scale * v1;
      out[1] = scale * v2;
      out[2] = scale * v3 * d;
      out[3] = scale * v4 * d;
      return out;
    }

    /**
     * Transforms the vec4 with a mat4.
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the vector to transform
     * @param {mat4} m matrix to transform with
     * @returns {vec4} out
     */
    export function transformMat4(out, a, m) {
      let x = a[0], y = a[1], z = a[2], w = a[3];
      out[0] = m[0] * x + m[4] * y + m[8] * z + m[12] * w;
      out[1] = m[1] * x + m[5] * y + m[9] * z + m[13] * w;
      out[2] = m[2] * x + m[6] * y + m[10] * z + m[14] * w;
      out[3] = m[3] * x + m[7] * y + m[11] * z + m[15] * w;
      return out;
    }

    /**
     * Transforms the vec4 with a quat
     *
     * @param {vec4} out the receiving vector
     * @param {vec4} a the vector to transform
     * @param {quat} q quaternion to transform with
     * @returns {vec4} out
     */
    export function transformQuat(out, a, q) {
      let x = a[0], y = a[1], z = a[2];
      let qx = q[0], qy = q[1], qz = q[2], qw = q[3];

      // calculate quat * vec
      let ix = qw * x + qy * z - qz * y;
      let iy = qw * y + qz * x - qx * z;
      let iz = qw * z + qx * y - qy * x;
      let iw = -qx * x - qy * y - qz * z;

      // calculate result * inverse quat
      out[0] = ix * qw + iw * -qx + iy * -qz - iz * -qy;
      out[1] = iy * qw + iw * -qy + iz * -qx - ix * -qz;
      out[2] = iz * qw + iw * -qz + ix * -qy - iy * -qx;
      out[3] = a[3];
      return out;
    }

    /**
     * Returns a string representation of a vector
     *
     * @param {vec4} a vector to represent as a string
     * @returns {String} string representation of the vector
     */
    export function str(a) {
      return 'vec4(' + a[0] + ', ' + a[1] + ', ' + a[2] + ', ' + a[3] + ')';
    }

    /**
     * Returns whether or not the vectors have exactly the same elements in the same position (when compared with ===)
     *
     * @param {vec4} a The first vector.
     * @param {vec4} b The second vector.
     * @returns {Boolean} True if the vectors are equal, false otherwise.
     */
    export function exactEquals(a, b) {
      return a[0] === b[0] && a[1] === b[1] && a[2] === b[2] && a[3] === b[3];
    }

    /**
     * Returns whether or not the vectors have approximately the same elements in the same position.
     *
     * @param {vec4} a The first vector.
     * @param {vec4} b The second vector.
     * @returns {Boolean} True if the vectors are equal, false otherwise.
     */
    export function equals(a, b) {
      let a0 = a[0], a1 = a[1], a2 = a[2], a3 = a[3];
      let b0 = b[0], b1 = b[1], b2 = b[2], b3 = b[3];
      return (Math.abs(a0 - b0) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a0), Math.abs(b0)) &&
              Math.abs(a1 - b1) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a1), Math.abs(b1)) &&
              Math.abs(a2 - b2) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a2), Math.abs(b2)) &&
              Math.abs(a3 - b3) <= glMatrix.EPSILON*Math.max(1.0, Math.abs(a3), Math.abs(b3)));
    }

    /**
     * Alias for {@link vec4.subtract}
     * @function
     */
    export const sub = subtract;

    /**
     * Alias for {@link vec4.multiply}
     * @function
     */
    export const mul = multiply;

    /**
     * Alias for {@link vec4.divide}
     * @function
     */
    export const div = divide;

    /**
     * Alias for {@link vec4.distance}
     * @function
     */
    export const dist = distance;

    /**
     * Alias for {@link vec4.squaredDistance}
     * @function
     */
    export const sqrDist = squaredDistance;

    /**
     * Alias for {@link vec4.length}
     * @function
     */
    export const len = length;

    /**
     * Alias for {@link vec4.squaredLength}
     * @function
     */
    export const sqrLen = squaredLength;

    /**
     * Perform some operation over an array of vec4s.
     *
     * @param {Array} a the array of vectors to iterate over
     * @param {Number} stride Number of elements between the start of each vec4. If 0 assumes tightly packed
     * @param {Number} offset Number of elements to skip at the beginning of the array
     * @param {Number} count Number of vec4s to iterate over. If 0 iterates over entire array
     * @param {Function} fn Function to call for each vector in the array
     * @param {Object} [arg] additional argument to pass to fn
     * @returns {Array} a
     * @function
     */
    export const forEach = (function() {
      let vec = create();

      return function(a, stride, offset, count, fn, arg) {
        let i, l;
        if(!stride) {
          stride = 4;
        }

        if(!offset) {
          offset = 0;
        }

        if(count) {
          l = Math.min((count * stride) + offset, a.length);
        } else {
          l = a.length;
        }

        for(i = offset; i < l; i += stride) {
          vec[0] = a[i]; vec[1] = a[i+1]; vec[2] = a[i+2]; vec[3] = a[i+3];
          fn(vec, vec, arg);
          a[i] = vec[0]; a[i+1] = vec[1]; a[i+2] = vec[2]; a[i+3] = vec[3];
        }

        return a;
      };
    })();