std::isdigit(std::locale)(3)

💅 std::isdigit(std::locale) 💅

okay bestie, this is the C++ Standard Libary manual page std::isdigit(std::locale)(3), and it's a cute little template that asks a locale whether a character counts as a digit. no cap. 🎀

✨ NAME ✨

std::isdigit(std::locale) - std::isdigit(std::locale)

Yes bestie, the NAME section is literally the function twice. iconic. 💀

🦋 Synopsis 🦋

Defined in header <locale>:

template< class CharT >
bool isdigit( CharT ch, const locale& loc );

It checks if the given character is classified as a digit by the given locale's std::ctype facet. that's the whole vibe. ✨

🌸 Parameters 🌸

• ch — character. the character we're vibe-checking 👀
• loc — locale. the locale doing the classifying 🫶

💖 Return value 💖

Returns true if the character is classified as a digit, false otherwise. periodt. ✅

🧚 Possible implementation 🧚

          template<class CharT>
          bool isdigit(CharT ch, const std::locale& loc)
          {
              return
       std::use_facet<std::ctype<CharT>>(loc).is(std::ctype_base::digit, ch);
          }

🔥 Example 🔥

okay here's the full code, bestie — run it and watch the locale do its thing:

       // Run this code

        #include <iostream>
        #include <locale>
        #include <string>
        #include <unordered_set>

        struct jdigit_ctype : std::ctype<wchar_t>
        {
            std::unordered_set<wchar_t> jdigits{
                L'一', L'二', L'三', L'四', L'五', L'六', L'七', L'八', L'九',
       L'十'
            };

            bool do_is(mask m, char_type c) const override
            {
                return (m & digit) && jdigits.contains(c)
                    ? true // Japanese digits will be classified as digits
                    : ctype::do_is(m, c); // leave the rest to the parent class
            }
        };

        int main()
        {
            std::wstring text = L"123一二三１２３";
            std::locale loc(std::locale(""), new jdigit_ctype);

            std::locale::global(std::locale("en_US.utf8"));
            std::wcout.imbue(std::locale());

            for (const wchar_t c : text)
                if (std::isdigit(c, loc))
                    std::wcout << c << " is a digit\n";
                else
                    std::wcout << c << " is NOT a digit\n";
        }

🍓 Possible output 🍓

        1 is a digit
        2 is a digit
        3 is a digit
        一 is a digit
        二 is a digit
        三 is a digit
        １ is NOT a digit
        ２ is NOT a digit
        ３ is NOT a digit

👑 See also 👑

• isdigit — checks if a character is a digit (function)
• iswdigit — checks if a wide character is a digit (function)

k bye bestie 💖 — source: http://cppreference.com, version/date: 2024.06.10, manual name: std::isdigit(std::locale)(3). slay and read the docs. ✨