std::isalnum(std::locale)

 

C++

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Technical specifications

Symbols index

External libraries

 

Localization library

Locales and facets
Locales
has_facet use_facet	locale
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
ctype facets
ctype ctype<char> ctype_byname	codecvt codecvt_byname
numeric facets
num_get num_put	numpunct numpunct_byname
collate facets
collate	collate_byname
time facets
time_get time_put	time_get_byname time_put_byname
monetary facets
money_get money_put	moneypunct moneypunct_byname
messages facets
messages	messages_byname

Character classification and conversion
Character classification
isspace isblank (C++11) iscntrl	isupper islower isalpha	ispunct isdigit isxdigit	isalnum isprint isgraph

Character conversions

toupper

tolower

String and stream conversions

wstring_convert (C++11/17/26*)

wbuffer_convert (C++11/17/26*)

Text encoding identifications

text_encoding (C++26)

Unicode conversion facets

codecvt_utf8 (C++11/17/26*)

codecvt_utf16 (C++11/17/26*)

codecvt_utf8_utf16 (C++11/17/26*)

codecvt_mode (C++11/17/26*)

C library locales
LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME	setlocale localeconv lconv

 

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

Checks if the given character is 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('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';
}

Possible output:

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

See also

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