Originally Posted by
kmdv
Because if Frota::lowestYear() is a const-qualified member function, then all member variables of *this (including "vehicles") are seen const-qualified as well. If you were able to use vector<Vehicle*>::iterator inside Frota::lowestYear() const then you could accidentally modify "vehicles", which would break the constness of "Frota". That was the cause, but apparently noone here has noticed it before.
