std::ios_base::fmtflags
科技促进发展：监督办[医]基：：fmt标志
| typedef /*implementation defined*/ fmtflags; | | |
|---|---|---|
| static constexpr fmtflags dec = /*implementation defined*/ static constexpr fmtflags oct = /*implementation defined*/ static constexpr fmtflags hex = /*implementation defined*/ static constexpr fmtflags basefield = /*implementation defined (dec | oct | hex)*/ | | |
| static constexpr fmtflags left = /*implementation defined*/ static constexpr fmtflags right = /*implementation defined*/ static constexpr fmtflags internal = /*implementation defined*/ static constexpr fmtflags adjustfield = /*implementation defined (left | right | internal)*/ | | |
| static constexpr fmtflags scientific = /*implementation defined*/ static constexpr fmtflags fixed = /*implementation defined*/ static constexpr fmtflags floatfield = /*implementation defined (scientific | fixed)*/ | | |
| static constexpr fmtflags boolalpha = /*implementation defined*/ static constexpr fmtflags showbase = /*implementation defined*/ static constexpr fmtflags showpoint = /*implementation defined*/ static constexpr fmtflags showpos = /*implementation defined*/ static constexpr fmtflags skipws = /*implementation defined*/ static constexpr fmtflags unitbuf = /*implementation defined*/ static constexpr fmtflags uppercase = /*implementation defined*/ | | |
指定可用的格式设置标志。这是一个BitmaskType.定义如下常数：
| 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 |
例
下面的示例显示了打印相同结果的几种不同方法。
二次
#include <iostream>
int main()
{
int num = 150;
// using fmtflags as class member constants:
std::cout.setf(std::ios_base::hex, std::ios_base::basefield
std::cout.setf(std::ios_base::showbase
std::cout << num << '\n';
// using fmtflags as inherited class member constants:
std::cout.setf (std::ios::hex , std::ios::basefield
std::cout.setf (std::ios::showbase
std::cout << num << '\n';
// using fmtflags as object member constants:
std::cout.setf(std::cout.hex, std::cout.basefield
std::cout.setf(std::cout.showbase
std::cout << num << '\n';
// using fmtflags as a type:
std::ios_base::fmtflags ff;
ff = std::cout.flags(
ff &= ~std::cout.basefield; // unset basefield bits
ff |= std::cout.hex; // set hex
ff |= std::cout.showbase; // set showbase
std::cout.flags(ff
std::cout << num << '\n';
// not using fmtflags, but using manipulators:
std::cout << std::hex << std::showbase << num << '\n';
}
二次
产出：
二次
0x96
0x96
0x96
0x96
0x96
二次
另见
| flags | manages format flags (public member function) |
|---|---|
| setf | sets specific format flag (public member function) |
| unsetf | clears specific format flag (public member function) |
| setbase | changes the base used for integer I/O (function) |
| setfill | changes the fill character (function template) |
| fixedscientifichexfloatdefaultfloat (C++11)(C++11) | changes formatting used for floating-point I/O (function) |
| showbasenoshowbase | controls whether prefix is used to indicate numeric base (function) |
| boolalphanoboolalpha | switches between textual and numeric representation of booleans (function) |
| showposnoshowpos | controls whether the + sign used with non-negative numbers (function) |
| showpointnoshowpoint | controls whether decimal point is always included in floating-point representation (function) |
| unitbufnounitbuf | controls whether output is flushed after each operation (function) |
| skipwsnoskipws | controls whether leading whitespace is skipped on input (function) |
| uppercasenouppercase | controls whether uppercase characters are used with some output formats (function) |
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