Flavio Castelli

How can you add regular expressions to C++?
Here you’re three small examples.

Pattern matching

In this example you’ll find how you can match a regexp in a string.

// Created by Flavio Castelli <flavio.castelli_AT_gmail.com>
// distrubuted under GPL v2 license

#include <boost/regex.hpp>
#include <string>

int main()
{
	boost::regex pattern ("bg|olug",boost::regex_constants::icase|boost::regex_constants::perl);
	std::string stringa ("Searching for BsLug");

	if (boost::regex_search (stringa, pattern, boost::regex_constants::format_perl))
		printf ("found\n");
	else
		printf("not found\n");
		
	return 0;
}

Substitutions

In this example you’ll find how you can replace a string matching a pattern.

// Created by Flavio Castelli <flavio.castelli@gmail.com>
// distrubuted under GPL v2 license

#include <boost/regex.hpp>
#include <string>

int main()
{
	boost::regex pattern ("b.lug",boost::regex_constants::icase|boost::regex_constants::perl);
	std::string stringa ("Searching for bolug");
	std::string replace ("BgLug");
	std::string newString;

	newString = boost::regex_replace (stringa, pattern, replace);

	printf("The new string is: |%s|\n",newString.c_str());
		
	return 0;
}

Split

In this example you’ll find how you tokenize a string with a pattern.

// Created by Flavio Castelli <flavio.castelli@gmail.com>
// distrubuted under GPL v2 license

#include <boost/regex.hpp>
#include <string>

int main()
{
	boost::regex pattern ("\\D",boost::regex_constants::icase|boost::regex_constants::perl);
	
	std::string stringa ("26/11/2005 17:30");
	std::string temp;
	
	boost::sregex_token_iterator i(stringa.begin(), stringa.end(), pattern, -1);
	boost::sregex_token_iterator j;

	unsigned int counter = 0;
	
	while(i != j)
	{
		temp = *i;
		printf ("token %i = |%s|\n", ++counter, temp.c_str());
		i++;
	}

	return 0;
}

Requirements

In order to build this examples you’ll need:

• a c++ compiler (like g++)
• boost regexp library

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This entry was posted on Thursday, February 16th, 2006 at 12:42 pm and is filed under C++, Howto. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.