std::ios_base::precision
streamsize precision() const; | (1) | |
streamsize precision( streamsize new_precision ); | (2) |
Manages the precision (i.e. how many digits are generated) of floating point output performed by std::num_put::do_put.
1) Returns the current precision.
2) Sets the precision to the given one. Returns the previous precision.
The default precision, as established by std::basic_ios::init, is 6.
Parameters
| new_precision | - | new precision setting |
Return value
The precision before the call to the function
Example
#include <iostream>
int main()
{
const double d = 12.345678901234;
std::cout << "The default precision is " << std::cout.precision() << "\n\n";
std::cout << "With default precision d is " << d << '\n';
std::cout.precision(8);
std::cout << "With high precision d is " << d << '\n';
}
Output:
The default precision is 6 With default precision d is 12.3457 With high precision d is 12.345679
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 189 | C++98 | 'precision' was defined as 'the number of digits after the decimal point', but it is not correct in some cases | corrected |
See also
| manages field width (public member function) |
|
| changes floating-point precision (function) |
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