Strange result with pow() function

[Itu]

Hello, I was recently making a convertor from number in base 10 to a binary number, and I ran into this problem:

(EXAMPLE CODE OF THE ISOLATED ISSUE)

#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;

int main()
{
    int exp = 2;
    int binary = 0;
    cout<<pow(10,exp)<<endl; //This will cout<< the number 100.
    binary += pow(10,exp);
    cout<<binary; //This will cout<< the number 99...
}

The pow function will return the number 100, but when adding the function to "binary", binary will become 99. Why does this happen? Any insight would be appreciated.

[3hM2Nwbp]

If I'd have to guess, I'd say that the problem would be floating point inaccuracy. Note the pow function:

double pow (double base, double exponent );
long double pow ( long double base, long double exponent );
float pow (float base, float exponent );
double pow (double base, int exponent );
long double pow (long double base, int exponent );

To resolve this, you may use the pow function in <complex> rather than math.h

[Itu]

Okay, thanks a lot Luc, I'll try that out.

[3hM2Nwbp]

The pow function is a template in <complex>, so you can hand it ints, long ints, or long long ints (*and more).