random_shuffle not allowing me to pass it a seed

Question

so I have a vector of cards and I'm trying to shuffle it using the random_shuffle method, but it's not shuffling them by only passing it the first and last item. So I know there's a third parameter which is a custom seed, the thing it, random_shuffle says it doesn't find any functions overloaded with these parameters (Or something like that - my program's in spanish)

Basically, I have two vectors, enemyCards and playerCards, both have a size of 5.

random_shuffle(enemyCards.begin(), enemyCards.end());
random_shuffle(playerCards.begin(), playerCards.end());

This compiles but is not working, while

int myrandom (int i)    { return std::rand()%i;}

random_shuffle(enemyCards.begin(), enemyCards.end(), myrandom);
random_shuffle(playerCards.begin(), playerCards.end(), myrandom);

doesn't even compile.

Am I doing something wrong?

I have a srand() at the beginning and other working rand() in the code, so the that should be working fine, it's just the random_shuffle that does not.

This is what the compiler says when using the myrandom method:

Error   11  error C3867: 'comgrid::Game::myrandom': function call missing argument list; use '&comgrid::Game::myrandom' to create a pointer to member
Error   12  error C2780: 'void _STL::random_shuffle(_RandomAccessIter,_RandomAccessIter)' : expects 2 arguments - 3 provided

Which is strange, because it's really 1:1 as the example on cplusplus.

Answer 1

Make myrandom a static member function of your Game class.

Answer 2

One does not pass a seed to random_shuffle: the optional third argument is a function object that must return a random integer in [0,n) when passed n as an argument. The following SSCCE demonstrates the use of random_shuffle (and the "better" C++11 variant shuffle) for your 5 element vectors (Live code at Coliru):

void dump_one(const char* name, vector<int> const& v) {
    cout << name << ": {" << v[0];
    for (auto i = size_t{1}; i < v.size(); ++i) {
        cout << ',' << v[i];
    }
    cout << "}\n";
}

int myrandom(int i) { return rand() % i; }

int main() {
    srand(random_device{}());
    auto playerCards = vector<int>{1,2,3,4,5};
    auto enemyCards  = vector<int>{6,7,8,9,10};

    // Variant 1: use std::rand
    random_shuffle(begin(playerCards), end(playerCards));
    random_shuffle(begin(enemyCards), end(enemyCards));
    dump_one("player", playerCards);
    dump_one("enemy", enemyCards);

    // Variant 2: use functor
    random_shuffle(begin(playerCards), end(playerCards), myrandom);
    random_shuffle(begin(enemyCards), end(enemyCards), myrandom);
    dump_one("player", playerCards);
    dump_one("enemy", enemyCards);

    // C++11: Use shuffle instead of random_shuffle
    auto engine = mt19937_64{random_device{}()};
    shuffle(begin(playerCards), end(playerCards), engine);
    shuffle(begin(enemyCards), end(enemyCards), engine);
    dump_one("player", playerCards);
    dump_one("enemy", enemyCards);
}

The techniques that you say "don't work" are working correctly, so the problem with your program is not in the things you are describing to us.