Setprecision is Confusing

Question

I just want to ask about setprecision because I\'m a bit confused.

here\'s the code:

#include 
#include 
using namesp         


        

Answer 1

There is no reason to expect that any of the constants in your post can be represented exactly using the floating-point system. As a consequence, the exact halves that you have may no longer be exact halves once you store them in a double variable (regardless of how the iostreams are meant to round such numbers.)

The following code illustrates my point:

#include 
#include 

using namespace std;

int main()

{
  double rate = 1.115;
  cout << fixed << setprecision(20) << rate;
}

Output:

1.11499999999999999112

I would recommend taking a look at the FAQ.