Re: overloading of ","

Adrian Hawryluk <>
Mon, 12 Mar 2007 19:31:36 GMT
Michael DOUBEZ wrote:

josh a ?crit :

Hi, I coded the following but It does not return what I expect, why?

#include <iostream>

using namespace std;

class Other
    int i;

    Other(int x=1)
        i = x;

    Other *operator-> () { return this;}

    Other &operator+ (Other t)
        i += t.i;

        return *this;

    Other &operator,(Other oth)
        i = oth.i;

        return *this;


int main()
    Other o0, o1, o2(4), o3(5);

    o0->i = 100;

    cout << o0.i << "\n" << o0->i << "\n";

       // HERE it returns 5 AND not 6 WHY ???????????????????
    Other ox = (o1 + o1, o3 = o2 + o1);

Because you have 5.
The expression evaluates:
Other ox = ( (o1 + o1) , (o3 = o2 + o1) );

Or with names
Other ox = o1.operator+(o1).operator,(o3.operator=(o2.operator+(o1)));

Since o3 is 5, then o1 is also 5 and ox is 5.

The reason is overloaded operator, doesn't have the same precedence as
POD operator,. Is is very confusing.

That is not the only thing confusing! Your use of operator,() is the so
obfuscated! Why on Earth would you want to do something like that?
What possible reason could you have?

On a side note, why isn't operator,() the same precedence as the regular
',' operator? I thought that all user defined operators had the same
precedence as the builtins.


           Adrian Hawryluk BSc. Computer Science
  Specialising in: OOD Methodologies in UML
                      OOP Methodologies in C, C++ and more
                                   RT Embedded Programming
  ----- [blog:] -----
   My newsgroup writings are licensed under the Creative
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