Question

I have two questions, the second being optional.
First, in the program below (a prototype of a simple card program), I am getting the following error:

(29): error C2660: ‘shuffle’ : function does not take 1 arguments
with the following code:

#include "stdafx.h"
#include <iostream>
#include <sstream>
#include <deque>
#include <algorithm>
using namespace std;

deque<int> cardDeck (51);
void flip(); //Prototype flip()
void shuffle(); //Prototype shuffle()

int _tmain(int argc, _TCHAR* argv[])
{
    ostream& operator<<(ostream& os, deque<int> dq); //overload << operator to accept deque 
                                                       //arguments
    for (int a=52; a>0; a--) { //initialize the 52 cards in a deck 
        cardDeck.push_front(a); 
    }
    flip(); //prompt my input to check data
    return 0;
}

void flip() { //flip over card in specified location in the deck
    int input;
    cin >> input;
    cout<<cardDeck[input]<<endl;
    shuffle(cardDeck);
    flip();
}

void shuffle(deque<int> dq) {  //use Fisher-Yates algorithm to efficiently and accurately 
                               //randomize card order
     for(int i=dq.size()-1; i>-1; i--) { 
         int j = rand() % (i + 1);
         if(i != j) {
             swap(dq[j], dq[i]);
         }
     }
}

Why do I receive this error? (I have looked around and attempted to solve it myself)

Secondly, I’m not certain if I’m doing the fisher-yates algorithm properly because c++ documentation isn’t easy to find on it (for the version that utilizes swap();) (Brownie points for answering this or pointing out any horribly awful coding practices, not including the lack of classes)

Thanks in advance!

Answer 1

The reason you get that error is because you declare shuffle as a function not taking any arguments.

void shuffle();

Another note is that you probably want to take a reference to the deque in that function, otherwise you’ll shuffle a local copy and won’t have the desired side effect.

You probably want it to lok like this:

void shuffle(deque<int>& dq);

Also, you might want to use iter_swap instead of swap to swap the elements. In a dequeue it probably won’t make a difference, but for list or map it would.