Can you make a C++ generic function?

Question

Is it possible to create a generic C++ function foo?

foo(Object bar, Object fred)
{
    //code
}

in which that if the two objects

Answer 1

OP seems to want to know if the 2 objects are comparable or not. You can use template specialization to achieve this (note: this doesn't compile on VC 10, but does on g++ 4.7). The only nuance, is you want this function to

they are compared and a comparison value is returned otherwise some other value is returned to indicate a comparison was not possible

But you need to define some sort of structure to signify that a comparison was not possible; using a magic number '-500' or whatever is not good style. Alternately, you could throw an error, and allow it to be caught an handled.

struct NoCompare{};

template 
static auto compare2(const U1 & u1, const U2 & u2) -> decltype(u1 == u2)
{ 
    cout << "Comparable" << endl;
    return u1 == u2;
}

static int compare2(...) 
{ 
    // Comparison not supported - return whatever value you want. (change the return type as appropriate)
    cout << "Not comparable" << endl;
    return -500;
}

int main()
{
    int a = 5, b = 3, c = 3;
    NoCompare dns;
    cout << compare2(a, b) << endl;
    cout << compare2(dns, b) << endl;
    cout << compare2(c, b) << endl;

    return 0;
}

Output: C:\MinGW\MinGW>a Comparable 0 Not comparable -500 Comparable 1