How to use the regex_iterator on data types of const char*/wchar_t*?

From docs:

using cregex_iterator = regex_iterator<const char*>;

using wcregex_iterator = regex_iterator<const wchar_t*>;

using sregex_iterator = regex_iteratorstring::const_iterator;

using wsregex_iterator = regex_iteratorwstring::const_iterator;

Reproducible example:

#include <string>
#include <iostream>
#include <regex>

template <typename T>
auto RegexMatchAll(const T* str, const T* regex)
{
    using iter = std::regex_iterator<T>;
    std::basic_regex<T> re(regex);
    auto words_begin = iter(str, (str   std::wcslen(str)), re); // <--- how to iterate according to the data in this case?
    auto words_end = iter();

    std::vector<std::match_results<iter>> result;

    for (iter i = words_begin; i != words_end;   i) {
         std::match_results<iter> m = *i;
         result.emplace_back(m);
    }  

    return result; 
}

int main() {
     auto matches = RegexMatchAll(L"10,20,30", LR"((\d ))"); 
}

CodePudding user response：

You have a few errors. Assuming you pass a const char* or const wchar_t*, T will be char or wchar_t, so:

• std::regex_iterator expects an iterator type, which neither char nor wchar_t are. You want to pass it const T* instead.
• *i will yeild a std::match_results<const T*> as well, so that's the type you should store in your result vector.
• std::wcslen is only good for T = wchar_t, you need to use std::strlen when T = char. I would create an overloaded wrapper function that calls the appropriate standard library function.

Putting that all together, something like this should work:

std::size_t str_len(const char* s) { return std::strlen(s); }
std::size_t str_len(const wchar_t* s) { return std::wcslen(s); }

template <typename T>
auto RegexMatchAll(const T* str, const T* regex)
{
    using iter = std::regex_iterator<const T*>;
    std::basic_regex<T> re(regex);
    auto words_begin = iter(str, str   str_len(str), re);
    auto words_end = iter();

    return std::vector<std::match_results<const T*>>(words_begin, words_end);
}

Demo

Note: I also simplified the std::vector construction to use its iterator pair constructor.