code: function copy(out, a) {
    out[0] = a[0]
    out[1] = a[1]
    out[2] = a[2]
    out[3] = a[3]
    return out
  }
docs: Copy the values from one mat2 to another
  
  @alias mat2.copy
  @param {mat2} out the receiving matrix
  @param {mat2} a the source matrix
  @returns {mat2} out