< 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.


[edit] Parameters

ch - character
loc - locale

[edit] Return value

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

[edit] 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);

[edit] 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);
    for (const wchar_t c : text)
        if (std::isdigit(c, loc))
            std::wcout << c << " is a digit\n";
            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

[edit] See also

checks if a character is a digit
(function) [edit]
checks if a wide character is a digit
(function) [edit]