Is there support in C++/STL for sorting objects by attribute?

Question

I wonder if there is support in STL for this:

Say I have an class like this :

class Person
{
public:
  int getAge() const;
  double getIncome() const         


        

Answer 1

I see that dribeas already posted that idea, but since I already wrote it, here's how you'd write a generic comparator to use getter functions.

#include 

template 
class CompareAttributeT: public std::binary_function
{
    typedef ResultType (Object::*Getter)() const;
    Getter getter;
public:
    CompareAttributeT(Getter method): getter(method) {}
    bool operator()(const Object* lhv, const Object* rhv) const
    {
        return (lhv->*getter)() < (rhv->*getter)();
    }
};

template 
CompareAttributeT CompareAttribute(ResultType (Object::*getter)() const)
{
    return CompareAttributeT(getter);
}

Usage:

std::sort(people.begin(), people.end(), CompareAttribute(&Person::getAge));

I think it might be a good idea to overload operator() for non-pointers, but then one couldn't typedef the argument_types by inheriting from binary_function - which is probably not a great loss, since it would hard to use it where those are needed anyway, for example, one just couldn't negate the comparison functor anyway.