What is the precision of long double in C++?

Question

Does anyone know how to find out the precision of long double on a specific platform? I appear to be losing precision after 17 decimal digits, which is the sa

Answer 1

You can find out with std::numeric_limits:

#include <iostream>     // std::cout
#include <limits>       // std::numeric_limits
int main(){
    std::cout << std::numeric_limits<long double>::digits10 << std::endl;
}

Answer 2

You can use <cfloat>. Specifically:

LDBL_DIG