Question

I am calculating square root of 2147483647 by sqrt function.and the result must be a float value 46340.95 but my code returns the value 46341.
Can anyone tell me where is the problem?
i am using code :

double x=2147483647.0;
double y=sqrt(x);
cout<< y;

Answer 1

I get that same result. But, if I inject a setprecision, I get the right value:

#include <iostream>
#include <iomanip>
#include <cmath>

int main (void) {
    double x=2147483647.0;
    double y=sqrt(x);
    std::cout << std::setprecision(10) << y << std::endl;
    return 0;
}

gives me:

46340.95

In fact, if you use the folowing code:

#include <iostream>
#include <iomanip>
#include <cmath>

int main (void) {
    double x=2147483647.0;
    double y=sqrt(x);
    std::cout << y << std::endl;
    std::cout << std::setprecision(0) << std::fixed << y << std::endl;
    std::cout << std::setprecision(1) << std::fixed << y << std::endl;
    std::cout << std::setprecision(2) << std::fixed << y << std::endl;
    std::cout << std::setprecision(3) << std::fixed << y << std::endl;
    return 0;
}

you get:

46341
46341
46341.0
46340.95
46340.950

So it appears that the default setting (at least for my environment) is a precision of zero.

If you want a specific format, I suggest you explicitly request it.