std::setprecision (3) Linux Manual Page

std::setprecision – std::setprecision

Synopsis

Defined in header<iomanip>

/*unspecified*/ setprecision(int n);

When used in an expression out << setprecision(n) or in >> setprecision(n), sets the precision parameter of the stream out or in to exactly n.

Parameters

n – new value for precision

Return value

Returns an object of unspecified type such that if str is the name of an output stream of type std::basic_ostream<CharT, Traits> or an input stream of type std::basic_istream<CharT, Traits>, then the expression str << setprecision(n) or str >> setprecision(n) behaves as if the following code was executed :

    str.precision(n);

Example

// Run this code

#include <iostream>

#include <iomanip>

#include <cmath>

#include <limits>

int main()

{
    const long double pi = std::acos(-1.L);
    std::cout << "default precision (6): " << pi << '\n'
              << "std::setprecision(10): " << std::setprecision(10) << pi << '\n'
              << "max precision:         "
              << std::setprecision(std::numeric_limits<long double>::digits10 + 1)
              << pi << '\n';
}

Output:

  default precision (6): 3.14159
  std::setprecision(10): 3.141592654
  max precision: 3.141592653589793239

See also

fixed
scientific
hexfloat
defaultfloat changes formatting used for floating-point I/O
             (function)
(C++11)
(C++11)
             manages decimal precision of floating point operations
precision (public member function of std::ios_base)