function
std::setprecision
/*unspecified*/ setprecision (int n);
Set decimal precision
Sets the
decimal precision to be used to format floating-point values on output operations.
Behaves as if member precision were called with n as argument on the stream on which it is inserted/extracted as a manipulator (it can be inserted/extracted on
input streams or
output streams).
This manipulator is declared in header
.
Parameters
-
n
-
New value for the
decimal precision.
Return Value
Unspecified. This function should only be used as a stream manipulator (see example).
Example
intput
// setprecision example
#include // std::cout, std::fixed
#include // std::setprecision
int main () {
double f =3.14159;
std::cout << std::setprecision(5) << f << '\n';
std::cout << std::setprecision(9) << f << '\n';
std::cout << std::fixed;
std::cout << std::setprecision(5) << f << '\n';
std::cout << std::setprecision(9) << f << '\n';
return 0;
}
Output:
3.1416
3.14159
3.14159
3.141590000
Data races
The stream object on which it is inserted/extracted is modified.
Concurrent access to the same stream object may introduce data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream is in a valid state.
See also
-
ios_base::precision
-
Get/Set floating-point decimal precision
(public member function)
-
fixed
-
Use fixed floating-point notation
(function)
-
scientific
-
Use scientific floating-point notation
(function)
http://www.cplusplus.com/reference/iomanip/setprecision/转至