< cpp‎ | locale
Defined in header <locale>
template< class charT >
bool isdigit( charT ch, const locale& loc );

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


ch - character
loc - locale

Return value

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

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);


#include <iostream>
#include <locale>
#include <string>
#include <set>
struct jdigit_ctype : std::ctype<wchar_t>
    std::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 {
        if ((m & digit) && jdigits.count(c))
            return true; // Japanese digits will be classified as digits
        return 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);
    for(wchar_t c : text)
        if(std::isdigit(c, loc))
            std::wcout << c << " is a digit\n";
            std::wcout << c << " is NOT a digit\n";


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

checks if a character is a digit
checks if a wide character is a digit