sub method
Subtract arg from this.
Implementation
void sub(Vector4 arg) {
final Float32List argStorage = arg._v4storage;
_v4storage[0] = _v4storage[0] - argStorage[0];
_v4storage[1] = _v4storage[1] - argStorage[1];
_v4storage[2] = _v4storage[2] - argStorage[2];
_v4storage[3] = _v4storage[3] - argStorage[3];
}