Question

I want to sort a vector using std::sort, but my sort method is a static method of a class, and I want to call std::sort outside it, but it seems to be trouble doing it this way.

On the class:

static int CompareIt(void *sol1, void *sol2) { ... }

std::sort call:

sort(distanceList.at(q).begin(), 
     distanceList.at(q).end(), 
     &DistanceNodeComparator::CompareIt);

Shouldn’t it be possible to do this way?

Answer 1

As others have mentioned, it needs a boolean return type. Here’s an example which works:

#include "stdafx.h"
#include <vector>
#include <algorithm>

using namespace std;

class MyClass
{
public:
    static bool CompareIt(const void *a1, const void *a2)
    {
        return a1 < a2;
    }
};


int _tmain(int argc, _TCHAR* argv[])
{

    // Create a vector that contains elements of type MyData
    vector<void*> myvector;

    // Add data to the vector
    myvector.push_back((void*)0x00000005);
    myvector.push_back((void*)0x00000001);

    // Sort the vector
    std::sort(myvector.begin(), myvector.end(), MyClass::CompareIt);

    // Display some results
    for( int i = 0; i < myvector.size(); i++ )
    {
        printf("%d = 0x%08X\n", i, myvector[i] );
    }

    return 0;
}

[Edit] Updated the code above to make it a little simpler. I’m not suggesting it’s nice code, but without know more about the OPs real implementation, it’s difficult to give a better example!