std::isdigit(std::locale)

Header: <locale>

Checks if the given character is classified as a digit by the given locale’s std::ctype facet.

# Declarations

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

# Parameters

# Return value

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

# Example

#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";
}

# See also