NAME¶

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

Synopsis¶

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.

Parameters¶

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);
}

Example¶

// 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)