I’m writing a C++ project and have a generic evaluate method in a class

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Asked: May 26, 20262026-05-26T08:05:58+00:00 2026-05-26T08:05:58+00:00

I’m writing a C++ project and have a generic evaluate method in a class

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I’m writing a C++ project and have a generic evaluate method in a class template.

My only question is how would I define the generateAllMoves and isPosFinal so that it is defined inside the classes that use this class template?

I’ve read that using pure virtual functions is a no no. I also do not want to make it static.

I foresee myself rewriting this as an abstract class, but then I would end up with a problem that requires generic types.

#ifndef ENGINE_H
#define ENGINE_H

#include <map>

using namespace std;

template< class M, class P >

class Engine {

public:

  Engine() { };  

  struct Move {
    P move;
    P pos;
    int score;
  };

  Move evaluate( P position ) {

    Move best;      

    if ( posIsFinal( position ) ) {
      Move newMove;
      newMove.pos = position;
      newMove.score = 1;
      return newMove;
    }

    else {

      map< M , P > allMoves = generateAllMoves( position );

      typename map< M , P > :: iterator it;

      for (it = allMoves.begin(); it != allMoves.end(); it++ ) {
        Move next = evaluate(it->second);

        if (next.score > best.score ) {
          best.pos = next.pos;
          best.move = next.move;
          best.score = next.score;
        }
      }
      return best;
    }
  }
};

#endif

Edit: To be more clear for everyone!

I have two different games right that defines its own generateAllMoves and isPosFinal methods. They use different algorithms and return different types…. For example, I will be soon implementing a chess game, but right now I’m implementing nim. Both interpret move and is this position final, differently.

2nd Edit:

Final code compiles!

#ifndef ENGINE_H
#define ENGINE_H

#include <map>

using namespace std;

template< typename Derived, class M, class P >

class Engine {

public:

  struct Move {
    P move;
    P pos;
    int score;
  };

  Move evaluate( P position ) {

    Move best;      

    if ( static_cast<Derived*>(this)->posIsFinal( position ) ) {
      Move newMove;
      newMove.pos = position;
      newMove.score = 1;
      return newMove;
    }

    else {

      map< M , P > allMoves = static_cast<Derived*>(this)->generateAllMoves( position );

      typename map< M , P > :: iterator it;

      for (it = allMoves.begin(); it != allMoves.end(); it++ ) {
        Move next = evaluate(it->second);

        if (next.score > best.score ) {
          best.pos = next.pos;
          best.move = next.move;
          best.score = next.score;
        }
      }
      return best;
    }
  }

  bool posIsFinal( P position ) {
    cerr << "Generic posIsFinal\n";
    exit(1);
  }

  map< M , P > generateAllMoves( P position ) {
    cerr << "Generic generateAllMoves\n";
    exit(1);
  }

private:


};

#endif