In C + +, regular expression syntax and common regular expression encyclopedia

The formal support for regular expressions in vc++2010 is undoubtedly a highlight of the vc++2010, bringing a lot of convenience to vs. C + + developers. Through their own use, the strong function of the regular expression is deeply felt. So summarize some simple introduction, and share with everybody.
One, what is a regular expression:
A regular expression (regular expression) is a "string" that describes a feature and then verifies that another "string" conforms to this feature. is a powerful tool for verifying and manipulating strings. A simple understanding of regular expressions can be considered a special validation string. For example, the expression "ab+" describes the characteristics of "a" and any ' B ', then ' ab ', ' ABB ', ' abbbbbbbbbb ' all conform to this feature.

Second, the regular expression can be used to do what.
Regular expressions can be used to:
(1) Verify that the string conforms to the specified characteristics, such as verifying that it is a legitimate mailing address.
(2) used to find strings, finding strings that match the specified characteristics from a long text, more flexible than finding a fixed string.
(3) Used to replace, more powerful than the ordinary replacement.

three, Introduction and basic grammar:

First look at a classic online example:

#include "stdafx.h"
#include <cstdlib>

#include <stdlib.h>

#include <boost/regex.hpp>

#include <string>

#include <iostream>

using namespace Std;

using namespace boost;

Regex expression ("^select" ([a-za-z]*) from ([a-za-z]*));

int main (int argc, char* argv[])

{

Std::string in;

Cmatch what;

cout << "Enter test string" << Endl;

Getline (Cin,in);

if (Regex_match (In.c_str (), what, expression))

{

for (int i=0;i<what.size (); i++)

cout<< "str:" <<what[i].str () <<endl;

}

Else

{

cout<< "Error Input" <<endl;

}

return 0;

}

Results

Enter: Select name from table

Output: Str:select name from table

Str:name
Str:table
According to our request, the strings are matched and singled out. This is useful when dealing with a large number of rules in text format, because it is flexible and Itong.
After reading the example, you have a perceptual understanding of the regular expression. So here are some basic syntax for regular expressions, with a set of grammar rules in regular expressions, common syntax including character matching, repeat matching, character positioning, escape matching, and other advanced syntax (character grouping, character substitution, and character decision):

character matching syntax:

character Syntax	syntax explanation	Syntax Example
//d	Matching numbers (0~9)	'//d ' match 8, no match;
//d	Match non-digit	'//d ' match C, does not match 3;
//w	Match any single character	'//w//w ' match A3, does not match @3;
//w	Match non-single character	'//w ' match @, do not match C;
//s	Match white space character	'//d//s//d ' match 3 D, does not match ABC;
//s	Match non-null characters	'//s//s//s ' match a#4, mismatch 3 D;
.	Matches any character	' ... ' matches a$ 5, does not match newline;