operator< comparing multiple fields

Question

I have the following operator< that is supposed to sort first by a value, then by another value:

    inline bool operator < (const obj& a, const ob         


        

Answer 1

You can use variadic templates in c++11 or later

template
bool less_than( const T& a, const T& b )
{
    return a < b;
}

template
bool less_than( const T& a, const T& b, Args... args )
(
    if ( a < b )
          return true;
    else if ( b < a )
          return false;
    else
          return less_than(  args...  );
)

Then you would call as

return less_than(a.x,b.x,
                 a.y,b.y,
                 a.z,b.z);

It supports any number of fields or types as long as type has < operator. You can mix types.