Comparison tricks in C++

Question

A class:

class foo{
public:
    int data;
};

Now I want to add a method to this class, to do some comparison, to see if its data is equal to on

Answer 1

It isn't pretty, but this should work:

class foo {
    bool equals(int a) { return a == data; }
    bool equals(int a, int b) { return (a == data) || (b == data); }
    bool equals(int a, int b, int c) {...}     
    bool equals(int a, int b, int c, int d) {...} 
private:
    int data; 
}

And so on. That'll give you the exact syntax you were after. But if you are after the completely variable number of arguments then either the vector, or std::initalizer list might be the way to go:

See: http://en.cppreference.com/w/cpp/utility/initializer_list

This example shows it in action:

#include 
#include 

class foo {
public:
        foo(int d) : data(d) {}
        bool equals_one_of(std::initializer_list options) {
                for (auto o: options) {
                        if (o == data) return true;
                }
                return false;
        }
private:
        int data;
};

int main() {
        foo f(10);
        assert(f.equals_one_of({1,3,5,7,8,10,14}));
        assert(!f.equals_one_of({3,6,14}));
        return 0;
}