function multiply$7(out, a, b) {
    var a0 = a[0],
        a1 = a[1],
        a2 = a[2],
        a3 = a[3],
        a4 = a[4],
        a5 = a[5];
    var b0 = b[0],
        b1 = b[1],
        b2 = b[2],
        b3 = b[3],
        b4 = b[4],
        b5 = b[5];
    out[0] = a0 * b0 + a2 * b1;
    out[1] = a1 * b0 + a3 * b1;
    out[2] = a0 * b2 + a2 * b3;
    out[3] = a1 * b2 + a3 * b3;
    out[4] = a0 * b4 + a2 * b5 + a4;
    out[5] = a1 * b4 + a3 * b5 + a5;
    return out;
  }
Multiplies two mat2d's

@param {mat2d} out the receiving matrix
@param {ReadonlyMat2d} a the first operand
@param {ReadonlyMat2d} b the second operand
@returns {mat2d} out