std::isalnum(std::locale)

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

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.

Parameters

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); }

Example

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

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

Output:

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

See also

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