std::isxdigit(std::locale)(3)

💖 std::isxdigit(std::locale)(3) 💖

okay so this page is from the C++ Standard Libary manual (yes, that's the spelling up top, bestie), section 3. It's all about the locale-flavored std::isxdigit check. iconic behavior, honestly. ✨

🌸 NAME 🌸

std::isxdigit(std::locale) — std::isxdigit(std::locale) 💅 (the name really is the thing twice, periodt).

✨ Synopsis ✨

Defined in header <locale>
template< class CharT >
bool isxdigit( CharT ch, const locale& loc );

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

🎀 Parameters 🎀

• ch — character
• loc — locale

💫 Return value 💫

Returns true if the character is classified as a hexadecimal digit, false otherwise. Simple slay.

🛠️ Possible implementation 🛠️

Here's one way it could look under the hood, no cap:

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

🌟 Example 🌟

okay bestie, run this code if you wanna see it in action:

// Run this code

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

struct gxdigit_ctype : std::ctype<wchar_t>
{
    std::unordered_set<wchar_t> greek_digits{L'α', L'β', L'γ', L'δ', L'ε', L'ζ'};

    bool do_is(mask m, char_type c) const override
    {
        return (m & xdigit) && greek_digits.contains(c)
            ? true // 6 first Greek small letters will be classified as digits
            : ctype::do_is(m, c); // leave the rest to the parent class
    }
};

int main()
{
    std::wstring text = L"0123456789abcdefABCDEFαβγδεζηθικλμ";
    std::locale loc(std::locale(""), new gxdigit_ctype);

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

    std::wcout << "Hexadecimal digits in text: ";
    for (const wchar_t c : text)
        if (std::isxdigit(c, loc))
            std::wcout << c << L' ';
    std::wcout << L'\n';

    std::wcout << "Not hexadecimal digits in text: ";
    for (const wchar_t c : text)
        if (not std::isxdigit(c, loc))
            std::wcout << c << L' ';
    std::wcout << L'\n';
}

🌈 Output 🌈

Hexadecimal digits in text: 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F α β γ δ ε ζ
Not hexadecimal digits in text: η θ ι κ λ μ

👀 See also 👀

go peek at these too:

• isxdigit — checks if a character is a hexadecimal character (function)
• iswxdigit — checks if a wide character is a hexadecimal character (function)

mwah 💋 — source/version/date tea: http://cppreference.com, 2024.06.10, page tag std::isxdigit(std::locale)(3). byeee bestie 🫶✨