C++ calculating more precise than double or long double

Question

I\'m teaching myself C++ and on this practice question it asks to write code that can calculate PI to >30 digits. I learned that double / long double are both 16 digits prec

Answer 1

You can use quad math, builtin type __float128 and q/Q suffixes in GCC/clang.

#include 

#include 

int main ()
{
  __float128 x = strtoflt128("1234567891234567891234567891234566", nullptr);
  auto y = 1.0q;
  printf("%.Qf", x + y); // there is quadmath_snprintf, but this also works fine
  return 0;
}