Overload an operator taking pointers in parameter

Question

I am trying to overload the '>' operator taking a pointer in parameter, however I get an error saying "operator > must have at least one parameter of type class". I do not get that error if I do not use pointer.

Note: S1 is a typedef'd structure, as well as elem.

bool operator>(S1 const *V1, S1 const *V2){
    if (V1->elem->code > V2->elem->code)
        return true;
    return false;
}

I use the operator in a case like this, for example :

S1 * funct(S1 *var1, S1 *var2){
    if (var1 > var2)
        return var1;
    return var2;
}

Why not make it use references and dereference the pointers for comparison? ie. if((*var1) > (*var2)) — GWW
– GWW, Commented Oct 12, 2011 at 1:44

Mankarse · Accepted Answer · 2011-10-12 07:36:40Z

2

This does not work because operator< is already defined for pointers. It is impossible to overload operators on built-in types because all of the operators that make sense for built-in types are already defined.

edited Oct 12, 2011 at 7:36

answered Oct 12, 2011 at 1:54

Mankarse

40.9k12 gold badges105 silver badges146 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

kylben · Accepted Answer · 2011-10-12 01:52:46Z

1

The compiler will want to turn your example into comparing the two pointer values. Having one parameter as a class type will tell it what it needs to know to resolve the overload.

bool operator>(const S1& V1, const S1& V2){
    if (V1.elem->code > V2.elem->code)
        return true;
    return false;
}

S1 * funct(S1 *var1, S1 *var2){
    if (*var1 > *var2)
        return var1;
    return var2;
}

Also, and I'm a bit rusty on this, but I think you have to declare the operator as a friend of S1, or make it a memeber.

answered Oct 12, 2011 at 1:52

kylben

3491 silver badge6 bronze badges

3 Comments

Mankarse Over a year ago

It does not need to be a friend or a member any more than any other function would. It only needs to be a friend if it attempts to access private or protected members of S1.

kylben Over a year ago

Ahh, OK, thanks, @Mankarse. It's been a while since I did one of these that wasn't a member.

MrRoy Over a year ago

I'm not sure about Mankarse's answer, but this solution seems to be working for me. Thanks

Peter O. · Accepted Answer · 2012-03-12 06:43:43Z

1

In my opinion, when you want to define a new operator which has more than one parameter.there are two things you must do.

Overload operator must be defined outside of the class.
The overload operator must be declared a friend functions or class of the class.

That's my experience.

edited Mar 12, 2012 at 6:43

Peter O.

33.1k14 gold badges86 silver badges97 bronze badges

answered Mar 12, 2012 at 6:19

kovenzhang

851 gold badge1 silver badge4 bronze badges

Collectives™ on Stack Overflow

Overload an operator taking pointers in parameter

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related