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    cpp/iterator/default sentinel t: Difference between revisions

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    →Example: adapting the regex example, it's a good example of a default constructed iterator as sentinel
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    m fmt.
     
    Line 21: Line 21:
    #include <regex>
    #include <regex>
    #include <string>
    #include <string>
     
    int main()
    int main()
    {
    {
         const std::string s = "Quick brown fox.";
         const std::string s = "Quick brown fox.";
     
         const std::regex words_regex("[^\\s]+");
         const std::regex words_regex("[^\\s]+");
         const std::ranges::subrange words(std::sregex_iterator(s.begin(), s.end(), words_regex), std::default_sentinel);
         const std::ranges::subrange words(
    std::sregex_iterator(s.begin(), s.end(), words_regex), std::default_sentinel);
         std::print("Found {} words:\n", std::ranges::distance(words));
     
         std::("Found {} words:", std::ranges::distance(words));
         for (const std::smatch& match : words)
         for (const std::smatch& match : words)
        {
             std::("{}", match.str());
             std::print("{}\n", match.str());
        }
    }
    }
    |output=
    |output=

    Latest revision as of 16:40, 21 February 2025

     
    C++
     
    Iterator library
    Iterator concepts
    Iterator primitives
    Algorithm concepts and utilities
    Indirect callable concepts
    Common algorithm requirements
    (C++20)
    (C++20)
    (C++20)
    Utilities
    (C++20)
    Iterator adaptors
    Range access
    (C++11)(C++14)
    (C++14)(C++14)  
    (C++11)(C++14)
    (C++14)(C++14)  
    (C++17)(C++20)
    (C++17)
    (C++17)
     
    Defined in header <iterator> 
    struct default_sentinel_t {};
    		(1) (since C++20) 
    inline constexpr default_sentinel_t default_sentinel{};
    		(2) (since C++20)
    1) default_sentinel_t is an empty class type used to denote the end of a range. It can be used together with iterator types that know the bound of their range (e.g., std::counted_iterator).
    2) default_sentinel is a constant of type default_sentinel_t.

    Example

    Run this code
    #include <print>
#include <regex>
#include <string>

int main()
{
    const std::string s = "Quick brown fox.";

    const std::regex words_regex("[^\\s]+");
    const std::ranges::subrange words(
        std::sregex_iterator(s.begin(), s.end(), words_regex), std::default_sentinel);

    std::println("Found {} words:", std::ranges::distance(words));
    for (const std::smatch& match : words)
        std::println("{}", match.str());
}

    Output: 

    Found 3 words:
Quick
brown
fox.

    See also

    		 input iterator that reads from std::basic_istream
    (class template) [edit]
    		input iterator that reads from std::basic_streambuf
    (class template) [edit]
    (C++20)
    		 iterator adaptor that tracks the distance to the end of the range
    (class template) [edit]