Question

I have a class with a few numeric fields such as:

class Class1 {
    int a;
    int b;
    int c;
public:
    // constructor and so on...
    bool operator<(const Class1& other) const;
};

I need to use objects of this class as a key in an std::map. I therefore implement operator<. What is the simplest implementation of operator< to use here?

EDIT:
The meaning of < can be assumed so as to guarantee uniqueness as long as any of the fields are unequal.

EDIT 2:

A simplistic implementation:

bool Class1::operator<(const Class1& other) const {
    if(a < other.a) return true;
    if(a > other.a) return false;

    if(b < other.b) return true;
    if(b > other.b) return false;

    if(c < other.c) return true;
    if(c > other.c) return false;

    return false;
}

The whole reason behind this post is just that I found the above implementation too verbose. There ought to be something simpler.

Answer 1

It depends on if the ordering is important to you in any way. If not, you could just do this:

bool operator<(const Class1& other) const
{
    if(a == other.a)
    {
         if(b == other.b)
         {
             return c < other.c;
         }
         else
         {
             return b < other.b;
         }
    }
    else
    {
        return a < other.a;
    }
}