[Boost] learning to use drip-1-Character Processing [by galphy]

[20050120]
1. character conversion
1.1 Related Classes
Lexical_cast
Bad_lexical_cast
1.2 definition file: # include <boost/lexical_cast.hpp>
1.3 features:
Used for type conversion. Conversion between strings and values
1.4 example:
Eclipse 3.0, gun g ++, and WINXP passed the test.
# Include <iostream>
# Include <boost/lexical_cast.hpp>

Using namespace STD;

Main ()
{
Int I = 100;
Char x pstr = "10101 ";
 
Cout <"before convert I is:" <I <Endl;
I = boost: lexical_cast <int> (pstr );
Cout <"after convert I is:" <I <Endl;
 
Return 0;
}
// Print: Before convert I is: 100
// After convert I is: 10101
 
1.5 others:
The exception handling for conversion is the same as that for general exception handling.
For example, try
{
// Convert
}
Catch (bad_lexical_cast &)
{
// Handle exceptions
}

2. format the string
2.1 related classes
Format
2.2 definition file: # include <boost/format. HPP>
2.3 features:
Construct a formatted string, some of which are to be determined and can be written as parameters.
2.4 example:
Eclipse 3.0, gun g ++, and WINXP passed the test.
# Include <iostream>
# Include <boost/format. HPP>
# Include <string>

Using namespace STD;

Using boost: format;
Using boost: IO: group;
Int main ()
{
Format FMT ("% 1% % 2% % 3% % 4% % 5% % 6%/N ");
// Replace the parameter with % 1%. 1 indicates the first parameter.
String STR;
Int I = 100;
Cout <FMT % 'G' % 'A' % 'l' % 'P' % 'H' % 'y' <Endl;
// % Operator press-in Parameter
String s_tmp = boost: STR (FMT );
// STR () free function, fomat-> string
// You can also use format. STR ();

Cout <s_tmp;
Return 0;
}
2.5 format description:
Use of "$": followed by the printf format Controller
"|" Usage: simplifies the control operator of the printf format
1. No Parameter order:
Format ("% 5d % 4 S % 5f"); // Add the printf format controller directly after %, and input parameters in sequence.
Format ("% | 5 | % | 4 | % | 5 |); // The effect is the same as the preceding one. The control symbols such as D, S, and F are automatically determined.
2. Parameter order:
Format ("% 1% % 2% % 1%");
Format ("% 1 $ 5d % 2 $5 S % 1 $ 5d );
Format ("% | 1 $5 | % | 2 $5 | % | 1 $5 |); // The effect is the same as above. The control symbols such as D, S, and F are automatically determined.
3. Specific format:

[N$] [Flags] [Width] [. Precision]Type-Char

• Flag	Meaning	Effect on internal stream
  '-'	Left alignment	N/A (applied later on the string)
  '='	Centered alignment	N/A (applied later on the string) -Note: added feature, not in printf-
  '_'	Internal alignment	Sets internal alignment -Note: added feature, not in printf-
  '+'	Show sign even for positive numbers	SetsShowpos
  '#'	Show numerical base, and decimal point	SetsShowbaseAndShowpoint
  '0'	Pad with 0's (inserted after sign or base indicator)	If not left-aligned, CILSSetfill ('0 ')And SetsInternal Extra actions are taken after Stream Conversion to handle user-defined output.
  ''	If the string does not begin+Or-, InsertSpaceBefore the converted string	N/A (applied later on the string) Different to printf's behaviour: it is not affected by internal alignment

• Type-Char	Meaning	Effect on stream
  P or X	Hexadecimal output	SetsHEX
  O	Octal output	SetsOct
  E	Scientific float format	Sets floatfield bitsScientific
  F	Fixed float format	Sets floatfield bitsFixed
  G	General-default-float format	UnsetAll floatfield bits
  X, EOrG	Same effect as their lowercase counterparts, but using uppercase letters for number outputs. (exponents, hex digits ,..)	Same Effects'X','E', Or'G',Plus Uppercase
  D, IOrU	DecimalType output	Sets basefield bitsDec
  SOrS	String output	PrecisionSpecification is unset, and its value goes to an internal field for later 'truncation'. (SeePrecisionExplicit)
  COrC	1-character output	Only the first character of the conversion string is used.
  %	Print the character%	N/