isIdentity method

bool isIdentity ()

Is this the identity matrix?

Implementation 

bool isIdentity() =>
    _m4storage[0] == 1.0 // col 1
    &&
    _m4storage[1] == 0.0 &&
    _m4storage[2] == 0.0 &&
    _m4storage[3] == 0.0 &&
    _m4storage[4] == 0.0 // col 2
    &&
    _m4storage[5] == 1.0 &&
    _m4storage[6] == 0.0 &&
    _m4storage[7] == 0.0 &&
    _m4storage[8] == 0.0 // col 3
    &&
    _m4storage[9] == 0.0 &&
    _m4storage[10] == 1.0 &&
    _m4storage[11] == 0.0 &&
    _m4storage[12] == 0.0 // col 4
    &&
    _m4storage[13] == 0.0 &&
    _m4storage[14] == 0.0 &&
    _m4storage[15] == 1.0;