C++头文件————iomanip

 

 

<iomanip>

IO Manipulators   //IO 操纵器

 

Header providing parametric manipulators:

头文件提供了参数化的操纵器，包括：

setiosflags

Set format flags (function )

resetiosflags

Reset format flags (function )

setbase

Set basefield flag (function )

setfill

Set fill character (function )

setprecision

Set decimal precision (function )

setw

Set field width (function )

get_money (C++11)

Get monetary value (function )

put_money (C++11)

Put monetary value (function )

get_time (C++11)

Get date and time (function )

put_time (C++11)

Put date and time (function )

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setiosflags-----------设置格式标志

Set format flags  

设置参数封装规范化格式标志

Example:

// setiosflags example
#include <iostream>     // std::cout, std::hex, std::endl
#include <iomanip>      // std::setiosflags

int main () {
  std::cout << std::hex;
  std::cout << std::setiosflags (std::ios::showbase | std::ios::uppercase);
  std::cout << 100 << std::endl;
  return 0;
}
//result: 0X64
//showbase:显示当前进制数（例中即0x），使用noshowbase可取消（则结果为：64）
//uppercase:以大写字母显示，即本来为（0x64），设置后变为（0X64）

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

resetiosflags-----重新设置格式标志

取消先前设置再进行新的格式设置

 

// resetiosflags example
#include <iostream>     // std::cout, std::hex, std::endl
#include <iomanip>      // std::setiosflags, std::resetiosflags

int main () {
  std::cout << std::hex << std::setiosflags (std::ios::showbase);
  std::cout << 100 << std::endl;
  std::cout << std::resetiosflags(std::ios::showbase) << 100 << std::endl;
  return 0;
}
//result:0x64  
//       64

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

setbase-----设置显示位制

Set basefield flag

 

// setbase example
#include <iostream>     // std::cout, std::endl
#include <iomanip>      // std::setbase

int main () {
  std::cout << std::setbase(16);
  std::cout << 110 << std::endl;
  return 0;
}
//result:6e
//110的16进制显示

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setfill-----设置填充字符

Set fill character

// setfill example
#include <iostream>     // std::cout, std::endl
#include <iomanip>      // std::setfill, std::setw

int main () {
  std::cout << std::setfill ('x') << std::setw (10);
  std::cout << 77 << std::endl;
  return 0;
}
//result:xxxxxxxx77
//setw：设置显示的位数为10
//77占两位，其余为字符x填充；

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

setprecision--设置显示精度

Set decimal （小数的）precision（精度）

// setprecision example
#include <iostream>     // std::cout, std::fixed
#include <iomanip>      // 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;
}
//3.1416 setprecision(5)
//3.14159 setprecision(9)
//3.14159
//3.141590000

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setw--设置区域宽度

Set field width

 

// setw example
#include <iostream>     // std::cout, std::endl
#include <iomanip>      // std::setw

int main () {
  std::cout << std::setw(10);
  std::cout << 77 << std::endl;
  return 0;
}
//result:       77 
//there are 8 spaces

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

get_money --获取货币输入

template <class moneyT>
/*unspecified*/ get_money (moneyT& mon, bool intl = false);

参数解释：

mon

Object where the monetary value is stored.
moneyT shall be either long double or a basic_string instantiation.

intl

true for international representations（国际单位）, false otherwise.
This is used internally（内部的） to instantiate（举例） the proper moneypunct class.

// get_money manipulator example
#include <iostream>     // std::cin, std::cout
#include <iomanip>      // std::get_money

int main ()
{
  long double price;
  std::cout << "Please, enter the price: ";
  std::cin >> std::get_money(price);

  if (std::cin.fail()) std::cout << "Error reading price\n";
  else std::cout << "The price entered is: " << price << '\n';

  return 0;
}

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

put_money 

Internally, the function accesses the output sequence by first constructing an object of type basic_ostream::sentry. Then (if evaluating the sentry object is true), it calls money_put::put (using the stream's selected locale) to perform both the formatting and the insertion operations, adjusting the stream's internal state flags accordingly. Finally, it destroys the sentry object before returning.

在内部，函数通过首先构造一个basic_ostream::sentry类型的对象来访问输出序列。然后(如果对sentry对象求值为true)，它调用money_put::put(使用流的选定区域设置)来执行格式化和插入操作，相应地调整流的内部状态标志。最后，它在返回之前销毁sentry对象。

template <class moneyT>
/*unspecified*/ put_money (const moneyT& mon, bool intl = false);

mon

Monetary value.
moneyT shall be either long double or a basic_string instantiation.

intl

true for international representations, false otherwise.
This is used internally to instantiate the proper moneypunct class.

// put_money manipulator example
#include <iostream>     // std::cout
#include <iomanip>      // std::put_money

int main ()
{
  std::cout << "Price:" << std::put_money(10.50L) << '\n';
  return 0;
}

 

 

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

get_time 

template <class charT>
/*unspecified*/ get_time (struct tm* tmb, const charT* fmt);

tmb

Pointer to an object of type struct tm where the time and date information extracted is stored.
struct tm is a class defined in header <ctime>.

指向存储时间和日期信息的tm结构的一个指针。tm结构在头文件ctime定义

fmt

C-string used by time_get::get as format string (see time_get::get).
charT is the character type in the c-string.

 

// get_time example
#include <iostream>     // std::cin, std::cout
#include <iomanip>      // std::get_time
#include <ctime>        // struct std::tm

int main ()
{
  struct std::tm when;
  std::cout << "Please, enter the time: ";
  std::cin >> std::get_time(&when,"%R");   // extract time (24H format)

  if (std::cin.fail()) std::cout << "Error reading time\n";
  else {
    std::cout << "The time entered is: ";
    std::cout << when.tm_hour << " hours and " << when.tm_min << " minutes\n";
  }

  return 0;
}

 

 

 

 

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

put_time 

Inserts the representation of the time and date information pointed by tmb, formatting it as specified by argument fmt.

按照fmt的所表达格式插入被tmb指向的时间和日期信息。

tmb

Pointer to the object of type struct tm with the date and time information to format.
struct tm is a class defined in header <ctime>.

fmt

C-string used by time_put::put as format string. It contains any combination of regular characters and special format specifiers. These format specifiers are replaced by the function to the corresponding values to represent the time specified in tmb. They all begin with a percentage (%) sign, and are:

specifier	Replaced by	Example
%a	Abbreviated weekday name *	Thu
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and time representation *	Thu Aug 23 14:55:02 2001
%C	Year divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Short MM/DD/YY date, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	Short YYYY-MM-DD date, equivalent to %Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%h	Abbreviated month name * (same as %b)	Aug
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%r	12-hour clock time *	02:55:02 pm
%R	24-hour HH:MM time, equivalent to %H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday as 1 (1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (00-53)	34
%w	Weekday as a decimal number with Sunday as 0 (0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%z	ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100) If timezone cannot be termined, no characters	+100
%Z	Timezone name or abbreviation * If timezone cannot be termined, no characters	CDT
%%	A % sign	%

* The specifiers marked with an asterisk (*) are locale-dependent.
Two locale-specific modifiers can also be inserted between the percentage sign (%) and the specifier proper to request an alternative format, where applicable:

Modifier	Meaning	Applies to
E	Uses the locale's alternative representation	%Ec %EC %Ex %EX %Ey %EY
O	Uses the locale's alternative numeric symbols	%Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy

charT is the character type in the c-string.

 

// put_time example
#include <iostream>     // std::cout
#include <iomanip>      // std::put_time
#include <ctime>        // std::time_t, struct std::tm, std::localtime
#include <chrono>       // std::chrono::system_clock

int main ()
{
  using std::chrono::system_clock;
  std::time_t tt = system_clock::to_time_t (system_clock::now());

  struct std::tm * ptm = std::localtime(&tt);
  std::cout << "Now (local time): " << std::put_time(ptm,"%c") << '\n';

  return 0;
}
//Now (local time): 03/07/13 11:41:34

 

 

翻译可能不尽得当，属于个人笔记，仅供参考

来源：http://www.cplusplus.com/reference/iomanip/