How to search for a regular expression in c++? - c++

I'm working on C++,
I need to search for a given regular expression in given string. Please provide me the pointer to do it. I tried to use boost::regex library.
Following is the regular expression:
regular expression to search : "get*"
And above expression i have to search in following different strings:
e.g.
1. "com::sun::star:getMethodName"
2. "com:sun:star::SetStatus"
3. "com::sun::star::getMessage"
so i above case i should get true for first string false for second and again true for third one.
Thanks in advance.

boost::regex re("get.+");
example.
#include <iostream>
#include <string>
#include <boost/regex.hpp>
#include <vector>
#include <algorithm>
int main()
{
std::vector<std::string> vec =
{
"com::sun::star:getMethodName",
"com:sun:star::SetStatus",
"com::sun::star::getMessage"
};
boost::regex re("get.+");
std::for_each(vec.begin(), vec.end(), [&re](const std::string& s)
{
boost::smatch match;
if (boost::regex_search(s, match, re))
{
std::cout << "Matched" << std::endl;
std::cout << match << std::endl;
}
});
}
http://liveworkspace.org/code/7d47ad340c497f7107f0890b62ffa609

Related

how connect regex replace to function in c++

#include <iostream>
#include <iterator>
#include <regex>
#include <string>
std::string ty(std::string text){
if(text == "brown")
return "true";
else
return "qw";
}
int main()
{
std::string text = "Quick $brown fox";
std::cout << '\n' << std::regex_replace(text, std::regex(R"(\\$(.*))"), ty("$&")) << '\n';
}
i use c++11 . I try without if worked but with if don't work ? i don't know what to do
There's a lot of different things wrong with the original code.
Firstly here's some working code
#include <iostream>
#include <iterator>
#include <regex>
#include <string>
std::string ty(std::string text){
if(text == "brown")
return "true";
else
return "qw";
}
int main()
{
std::string text = "Quick $brown fox";
std::smatch m;
if (std::regex_search(text, m, std::regex(R"(\$([[:alpha:]][[:alnum:]]*))")))
{
std::cout << '\n' << ty(std::string(m[1].first, m[1].second)) << '\n';
}
else
{
std::cout << "\nno match\n";
}
}
Some things that were wrong with the original code
Firstly the function being called was wrong. Use std::regex_search to search for matches in a string. Capture the results in an std::smatch object and then use those results to call the ty function.
The regex was wrong in two different ways. Firstly \\ is wrong because you are using a raw string literal, so only a single backslash is required. Secondly (.*) is wrong because that will match the entire rest of the string. You only want to match the word following the dollar. I've used ([[:alpha:]][[:alnum:]]*) instead. That might not be exactly what you want but it works for this example. You can modify it if you want.

pattern search in text strings in c++

I just want look for a pattern in a string. for example for this "abaxavabaabcabbc" string the app should print "abc" and "abbc". So, the pattern should have "abc" but the numbers of "b" are changing.
pattern => "abc" => the numbers of "b" are changeable.
And the programm should be in c++.
Using regex_search instead of the iterator:
Live On Coliru
#include <regex>
#include <string>
#include <iostream>
int main() {
std::regex const pattern("ab+c");
for (std::string const text :
{
"abaxavabaabcabbc",
}) //
{
std::smatch match;
for (auto it = text.cbegin(), e = text.cend();
std::regex_search(it, e, match, pattern); it = match[0].second) {
std::cout << "Match: " << match.str() << "\n";
}
}
}
Prints
Match: abc
Match: abbc
There is only one answer to this question. You MUST use a std::regex. Regular expressions are exactly made for this purpose.
C++ supports also regular expressions. Please see here
The regex "ab+c" will match all strings starting with an "a", having one or more "b" and end with a "c"
See the following very short program:
#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
#include <regex>
const std::regex re{ R"(ab+c)" };
using Iter = std::sregex_token_iterator;
int main() {
const std::string test{ "abaxavabaabcabbc" };
std::copy(Iter(test.begin(), test.end(), re), Iter(), std::ostream_iterator<std::string>(std::cout, "\n"));
}
This program will iterate over all matched patterns and copy them to std::cout

how to use Boost regular expression replace method?

I have these variables:
boost::regex re //regular expression to use
std::string stringToChange //replace this string
std::string newValue //new value that is going to replace the stringToChange depending on the regex.
I only want to replace the first occurrence of it only.
Thanks fellas.
EDIT: I've found this:
boost::regex_replace(stringToChange, re, boost::format_first_only);
but it says the function does not exists, I'm guessing the parameters are incorrect at the moment.
Here is an example of basic usage:
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main(){
std::string str = "hellooooooooo";
std::string newtext = "o Bob";
boost::regex re("ooooooooo");
std::cout << str << std::endl;
std::string result = boost::regex_replace(str, re, newtext);
std::cout << result << std::endl;
}
Output
hellooooooooo
hello Bob
Make sure you are including <boost/regex.hpp> and have linked to the boost_regex library.

How do I get the regex matched value using Boost.Regex?

I'm trying to extract the domain from a URL. Following is an example script.
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main () {
std::string url = "http://mydomain.com/randompage.php";
boost::regex exp("^https?://([^/]*?)/");
std::cout << regex_search(url,exp);
}
How do I print the matched value?
You need to use the overload of regex_search that takes a match_results object. In your case:
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main () {
std::string url = "http://mydomain.com/randompage.php";
boost::regex exp("^https?://([^/]*?)/");
boost::smatch match;
if (boost::regex_search(url, match, exp))
{
std::cout << std::string(match[1].first, match[1].second);
}
}
Edit: Corrected begin, end ==> first, second

If-Then-Else Conditionals in Regular Expressions and using capturing group

I have some difficulties in understanding if-then-else conditionals in regular expressions.
After reading If-Then-Else Conditionals in Regular Expressions I decided to write a simple test. I use C++, Boost 1.38 Regex and MS VC 8.0.
I have written this program:
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main()
{
std::string str_to_modify = "123";
//std::string str_to_modify = "ttt";
boost::regex regex_to_search ("(\\d\\d\\d)");
std::string regex_format ("(?($1)$1|000)");
std::string modified_str =
boost::regex_replace(
str_to_modify,
regex_to_search,
regex_format,
boost::match_default | boost::format_all | format_no_copy );
std::cout << modified_str << std::endl;
return 0;
}
I expected to get "123" if str_to_modify has "123" and to get "000" if I str_to_modify has "ttt". However I get ?123123|000 in the first case and nothing in second one.
Coluld you tell me, please, what is wrong with my test?
The second example that still doesn't work :
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main()
{
//std::string str_to_modify = "123";
std::string str_to_modify = "ttt";
boost::regex regex_to_search ("(\\d\\d\\d)");
std::string regex_format ("(?1foo:bar");
std::string modified_str =
boost::regex_replace(str_to_modify, regex_to_search, regex_format,
boost::match_default | boost::format_all | boost::format_no_copy );
std::cout << modified_str << std::endl;
return 0;
}
I think the format string should be (?1$1:000) as described in the Boost.Regex docs.
Edit: I don't think regex_replace can do what you want. Why don't you try the following instead? regex_match will tell you whether the match succeeded (or you can use match[i].matched to check whether the i-th tagged sub-expression matched). You can format the match using the match.format member function.
#include <iostream>
#include <string>
#include <boost/regex.hpp>
int main()
{
boost::regex regex_to_search ("(\\d\\d\\d)");
std::string str_to_modify;
while (std::getline(std::cin, str_to_modify))
{
boost::smatch match;
if (boost::regex_match(str_to_modify, match, regex_to_search))
std::cout << match.format("foo:$1") << std::endl;
else
std::cout << "error" << std::endl;
}
}