std::ios_base::setf

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

将格式化标志设置为指定的设置。

1%29设置由flags有效地执行以下操作fl = fl | flags何地fl定义内部格式标志的状态。

2%29清除下面的格式标志mask，并将已清除的标志设置为flags有效地执行以下操作fl = (fl & ~mask) | (flags & mask)何地fl定义内部格式标志的状态。

参数

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 following constants: 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\|0. 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\|(scientific\|fixed)\|0. 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 uppercaseequivalents in certain output output operations: see std::uppercase	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\|0. 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\|(scientific\|fixed)\|0. 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 uppercaseequivalents in certain output output operations: see std::uppercase
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\|0. 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\|(scientific\|fixed)\|0. 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 uppercaseequivalents in certain output output operations: see std::uppercase

返回值

调用函数之前的格式标志。

例

二次

#include <iostream>
#include <iomanip>
 
const double PI = 3.1415926535;
 
int main() 
{
    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);
    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';
    }
}

二次

产出：

二次

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

二次

另见

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

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最后更新于：2017-12-18