sub method
Subtract o
from this.
Implementation
void sub(Matrix2 o) {
final oStorage = o._m2storage;
_m2storage[0] = _m2storage[0] - oStorage[0];
_m2storage[1] = _m2storage[1] - oStorage[1];
_m2storage[2] = _m2storage[2] - oStorage[2];
_m2storage[3] = _m2storage[3] - oStorage[3];
}