assert function?

[PeiFeng]

my question is about the assert() with
the following code:

#include "stdafx.h"
#include <iostream>
#include <string>
#include <algorithm>
#include <conio.h>
#include <set>
#include <assert.h>

typedef set<int> intSet;


int main(int argc, char* argv[])
{
intSet::_Pairib pib;


for (int i=0;i<1000;i++)
//assert( s1.insert(ID("xie",i)).second );
{
pib=s1.insert(ID("xie",i));
assert(pib.second);
}


..................
getch();

return 0;
}


it works OK!
but why i cant used the assert statement?
i think it's equal to the statements in the brace!

[dude_1967]

Victory,

The compressed single line should give the same functionality as the expanded two lines. I would put the single line in braces for clarity.

Sincerely, Chris.

#include <iostream>
#include <string>
#include <algorithm>
#include <conio.h>
#include <set>
#include <cassert>

using namespace std;

typedef set<int> intSet;

intSet s1;

#define ID(a, b) 3

int main(int argc, char* argv[])
{
  intSet::_Pairib pib;

  for(int i = 0; i < 1000; i++)
  {
    assert( s1.insert(ID("xie",i)).second );
//    pib = s1.insert(ID("xie",i));
//    assert(pib.second);
  }

  return 1;
}

[Graham]

Except, of course, that when you compile for release mode, the expression in the assert statement will not get executed.

The two versions are not equivalent, and the single-statement version will lead to problems. Never put code with side-effects into an assert, only examine data.

[dude_1967]

Oh yeah,

I guess I had forgotten that assert code might not even get compiled under most conditions. This wouldn't work very well...

Thanks for that key reminder Graham.

Maybe it would be better to store second.pib in an intermediate variable and assert the variable.

Sincerely, Chris.

[Graham]

Of course, up to this point, I've refrained from wondering why on earth this code is reliant on a detail of one particular STL implementation. _Pairib is not part of the standard interface to std::set (the leading underscore is a dead giveaway) and you have to wonder why any piece of code would need to bother with it.

[PeiFeng]

Graham,Thank you for your advice

Originally posted by Graham
Never put code with side-effects into an assert, only examine data.

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