BFE>template< class  launcher>
BFE>class launcher_commander {
BFE> launcher& launcher_;
BFE>public:
BFE>  void run() {
BFE>    while(...) {
BFE>      if(target_detected()) launcher_.launch_rockets();
BFE>      ...
BFE>    }
BFE>  }
BFE>};

BFE>class vehicle_based_launcher {
BFE>   void launch_rockets() { .... }
BFE>};

BFE>class ship_based_launcher {
BFE>   void launch_rockets() { .... }
BFE>};

BFE>#if VEHICLE_BUILD
BFE>typedef  vehicle_based_launcher TLauncher;
BFE>#else if SHIP_BUILD
BFE>typedef  ship_based_launcher TLauncher;
BFE>#else ...
BFE>#endif

BFE>int main() {
BFE>  TLauncher launcher{...};

BFE>  launcher_commander<TLauncher> commander{launcher};
BFE>  commander.run();
BFE>  ...
BFE>}
BFE>