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

std::isalnum(std::locale): std::isalnum(std::locale)


std::isalnum(std::locale) - std::isalnum(std::locale)


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

Checks if the given character classified as an alphanumeric character by the given locale's std::ctype facet.


ch - character
loc - locale

Return value

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

Possible implementation

  template< class charT >
  bool isalnum( charT ch, const std::locale& loc ) {
      return std::use_facet<std::ctype<charT>>(loc).is(std::ctype_base::alnum, ch);


Demonstrates the use of isalnum() with different locales (OS-specific).
// Run this code

  #include <iostream>
  #include <locale>
  int main()
      const wchar_t c = L'\u2135'; // mathematical symbol aleph

      std::locale loc1("C");
      std::cout << "isalnum('ℵ', C locale) returned "
                 << std::boolalpha << std::isalnum(c, loc1) << '\n';

      std::locale loc2("en_US.UTF-8");
      std::cout << "isalnum('ℵ', Unicode locale) returned "
                << std::boolalpha << std::isalnum(c, loc2) << '\n';


  isalnum('ℵ', C locale) returned false
  isalnum('ℵ', Unicode locale) returned true

See also

         checks if a character is alphanumeric
isalnum (function)
         checks if a wide character is alphanumeric
iswalnum (function)