c++ division by 0

I am running long simulations. I record the results into a vector to compute statistics about the data. I realized that, in theory, those samples could开发者_JAVA百科 be the result of a division by zero; this is only theoretical, I am pretty sure it's not the case. In order to avoid rerunning the simulation after modifying the code, I was wondering what happens in that case. Would I be able to realize whether a division by 0 has occurred or not? Will I get error messages? (Exceptions are not being handled at the moment).

Thanks

For IEEE floats, division of a finite nonzero float by 0 is well-defined and results in +infinity (if the value was >zero) or -infinity (if the value was less than zero). The result of 0.0/0.0 is NaN. If you use integers, the behaviour is undefined.

Note that C standard says (6.5.5):

The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined.

So something/0 is undefined (by the standard) both for integral types and Floating points. Nevertheless most implementations have fore mentioned behavior (+-INF or NAN).

If you're talking integers then your program should crash upon division by zero.

If you're talking floats then division by zero is allowed and the result to that is INF or -INF. Now it's all up to your code if the program will crash, handle that nicely or continue with undefined/unexpected results.

If you use IEEE floats, then it will return 0 or NaN. If the op1 is 0, you will get undefined. If op1 is higher than 0, you will get Infinity. If op1 is lower than 0, then you will get -Infinity. If you use dividing by 0 directly or in integer , you will get error "Floating point exception".

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
    double a = 123, b = 0;
    double result = a/b;

    string isInfinite = isinf(result) ? "is" : "is not";
    cout << "result=" << result << " " << isInfinite << " infinity" << endl;
}

result=inf is infinity