NAME¶

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