std::isdigit(std::locale) (3) - Linux Manuals

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

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 <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);

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

      for(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";
  }

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