Question

I have defined the classes ‘Outcome’ and ‘Bin’.
I am trying to pass an array of type Outcome to a Bin Constructor, in order to add each element of that array to a set of ‘Outcome’s that is a member property of the Bin Class.

//Bin.h
class Bin {
private:
    std::set<Outcome> outcomeset;
public:
    Bin();
    Bin(Outcome Outcs[], int numberofelements);
    Bin(std::set<Outcome> Outcs);
    void add(Outcome Outc);
    std::string read();

};

//In Bin.cpp

Bin::Bin(Outcome outcs[], int numberofelements) {
    int i;
    for (i=0;i<(numberofelements-1);i++) {
        outcomeset.insert(outcs[i]); //When this LIne is commented out, no compile errors!
    }
}

This results in a whole mess of errors in VS2010 that link back to library files. I have been unable to find anything online or in my “The Big C++” textbook. Is this a completely wrong implementation of this sort of functionality? Or am I missing something rather basic?

For the curious I am implementing this as part of the ‘Roulette’ Problem from this free textbook http://www.itmaybeahack.com/homepage/books/oodesign.html

Thanks for your help!

EDIT: I have added the (rather lengthy) error text to a pastebin, here: http://pastebin.com/cqe0KF3K

EDIT2: I have implemented the == != and < operators for the outcome class, and the same line still does not compile. Here are the implementations

//Outcome.cpp
bool Outcome::operator==(Outcome compoutc) {
    if (mEqual(compoutc) == true) {
    return true;
}
else {
    return false;
}
}

bool Outcome::operator!=(Outcome compoutc) {
if (mEqual(compoutc) == false) {
    return true;
}
else {
    return false;
}
}

bool Outcome::operator<(Outcome compoutc) {
if (odds < compoutc.odds) {
    return true;
}
else {
    return false;
}
}

EDIT3: Implemented the comparison operator with the de-referenced parameter and const tags and now it compiles!

Answer 1

You need to define an operator< for the class being inserted into the set.

Also note that instead of an explicit loop, you’re probably better off using a pair of “iterators” (pointers, in this case) and actually initializing the set:

#include <set>
#include <string>

class Outcome { 
    int val;
public:
    bool operator<(Outcome const &other) const { 
        return val < other.val;
    }
    Outcome(int v = 0) : val(v) {}
};

class Bin {
private:
    std::set<Outcome> outcomeset;
public:
    Bin();

    // Actually initialize the set:
    Bin(Outcome Outcs[], int n) : outcomeset(Outcs, Outcs+n) {}
    Bin(std::set<Outcome> Outcs);
    void add(Outcome Outc);
    std::string read();

};

int main() { 
    // Create an array of Outcomes
    Outcome outcomes[] = {Outcome(0), Outcome(1) };

    // use them to initialize the bin:
    Bin b((outcomes),2);

    return 0;
}