std::ios_base::setf

 

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fmtflags setf( fmtflags flags );	(1)
fmtflags setf( fmtflags flags, fmtflags mask );	(2)

Sets the formatting flags to specified settings.

1) Sets the formatting flags identified by flags. Effectively, the following operation is performed fl = fl | flags where fl defines the state of internal formatting flags.

2) Clears the formatting flags under mask, and sets the cleared flags to those specified by flags. Effectively the following operation is performed fl = (fl & ~mask) | (flags & mask) where fl defines the state of internal formatting flags.

Parameters

flags, mask

-

new formatting setting. mask defines which flags can be altered, flags defines which flags of those to be altered should be set (others will be cleared). Both parameters can be a combination of the formatting flags constants

Formatting flags

Constant	Explanation
dec	use decimal base for integer I/O: see std::dec
oct	use octal base for integer I/O: see std::oct
hex	use hexadecimal base for integer I/O: see std::hex
basefield	dec | oct | hex. Useful for masking operations
left	left adjustment (adds fill characters to the right): see std::left
right	right adjustment (adds fill characters to the left): see std::right
internal	internal adjustment (adds fill characters to the internal designated point): see std::internal
adjustfield	left | right | internal. Useful for masking operations
scientific	generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific
fixed	generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed
floatfield	scientific | fixed. Useful for masking operations
boolalpha	insert and extract bool type in alphanumeric format: see std::boolalpha
showbase	generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase
showpoint	generate a decimal-point character unconditionally for floating-point number output: see std::showpoint
showpos	generate a + character for non-negative numeric output: see std::showpos
skipws	skip leading whitespace before certain input operations: see std::skipws
unitbuf	flush the output after each output operation: see std::unitbuf
uppercase	replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase

Return value

The formatting flags before the call to the function.

Example

Run this code

#include <iomanip>
#include <iostream>
#include <numbers>
 
int main()
{
    const double PI = std::numbers::pi;
    const int WIDTH = 15;
 
    std::cout.setf(std::ios::right); // equivalent: cout << right;
    std::cout << std::setw(WIDTH / 2) << "radius"
              << std::setw(WIDTH) << "circumference" << '\n';
 
    std::cout.setf(std::ios::fixed); // equivalent: cout << fixed;
    for (double radius = 1; radius <= 6; radius += 0.5)
        std::cout << std::setprecision(1) << std::setw(WIDTH / 2)
                  << radius
                  << std::setprecision(2) << std::setw(WIDTH)
                  << (2 * PI * radius) << '\n';
}

Output:

 radius  circumference
    1.0           6.28
    1.5           9.42
    2.0          12.57
    2.5          15.71
    3.0          18.85
    3.5          21.99
    4.0          25.13
    4.5          28.27
    5.0          31.42
    5.5          34.56
    6.0          37.70

See also

flags	manages format flags (public member function)
unsetf	clears specific format flag (public member function)