std::isalnum

 

C++

语言

概念

实用工具库

字符串库

集装箱库

算法库

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正则表达式库 （C++11）

原子操作库 （C++11）

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字符串库

null结尾的字符串 Original: Null-terminated strings The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

字节的字符串

多字节字符串

宽字符串

类 Original: Classes The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

basic_string

char_traits

 

NULL结尾的字节串

功能 Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
字符操作 Original: Character manipulation The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
isalnum isalpha islower isupper isdigit isxdigit isblank （C++11）	iscntrl isgraph isspace isprint ispunct tolower toupper
转换为数字格式 Original: Conversions to numeric formats The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
atof atoi atol atoll strtol strtoll	strtoul strtoull strtof strtod strtold
字符串操作 Original: String manipulation The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
strcpy
strncpy
strcat
strncat
strxfrm
字符串检查 Original: String examination The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
strlen strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtok
内存操作 Original: Memory manipulation The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
memchr
memcmp
memset
memcpy
memmove
杂项 Original: Miscellaneous The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
strerror

 

Defined in header <cctype>
int isalnum( int ch );

检查是否给定的字符是字母数字字符，根据当前的C语言环境，即（0123456789在默认的语言环境），大写字母（ABCDEFGHIJKLMNOPQRSTUVWXYZ在默认的语言环境），或一个小写字母（abcdefghijklmnopqrstuvwxyz默认区域中）.

Original:

Checks if the given character is an alphanumeric character according to the current C locale, i.e. either a number (0123456789 in the default locale), an uppercase letter (ABCDEFGHIJKLMNOPQRSTUVWXYZ in the default locale), or a lowercase letter (abcdefghijklmnopqrstuvwxyz in the default locale).

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参数

ch

-

字符 Original: character The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

返回值

非0值（true），如果字符是字母数字字符，0（false），否则.

Original:

Non-zero value (true) if the character is an alphanumeric character, 0 (false) otherwise.

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为例

演示isalnum（）使用不同的语言环境（OS特定）.

Original:

Demonstrates the use of isalnum() with different locales (OS-specific).

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#include <iostream>
#include <cctype>
#include <clocale>
 
int main()
{
    const char c = '\xdf'; // German letter ß in ISO-8859-1
 
    std::cout << "isalnum(\'\\xdf\', default C locale) returned "
               << std::boolalpha << (bool)std::isalnum(c) << '\n';
 
    std::setlocale(LC_ALL, "de_DE.iso88591");
    std::cout << "isalnum(\'\\xdf\', ISO-8859-1 locale) returned "
              << std::boolalpha << (bool)std::isalnum(c) << '\n';
 
}

Output:

isalnum('\xdf', default C locale) returned false
isalnum('\xdf', ISO-8859-1 locale) returned true

另请参阅

isalnum(std::locale)	被列为检查，如果一个字符的字母数字的语言环境 Original: checks if a character is classified as alphanumeric by a locale The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）
iswalnum	检查是否使用了一个宽字符是字母数字 Original: checks if a wide character is alphanumeric The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数）
C documentation for isalnum

ASCII values (hex)		characters	iscntrl iswcntrl	isprint iswprint	isspace iswspace	isblank iswblank	isgraph iswgraph	ispunct iswpunct	isalnum iswalnum	isalpha iswalpha	isupper iswupper	islower iswlower	isdigit iswdigit	isxdigit iswxdigit
0 - 8	0x00-0x08	control codes (NUL, etc.)	≠0	0	0	0	0	0	0	0	0	0	0	0
9	0x09	tab (\t)	≠0	0	≠0	≠0	0	0	0	0	0	0	0	0
10 - 13	0x0A-0x0D	whitespaces (\n,\v,\f,\r)	≠0	0	≠0	0	0	0	0	0	0	0	0	0
14 - 31	0x0E-0x1F	control codes	≠0	0	0	0	0	0	0	0	0	0	0	0
32	0x20	space	0	≠0	≠0	≠0	0	0	0	0	0	0	0	0
33 - 47	0x21-0x2F	!"#$%&'()*+,-./	0	≠0	0	0	≠0	≠0	0	0	0	0	0	0
48 - 57	0x30-0x39	0123456789	0	≠0	0	0	≠0	0	≠0	0	0	0	≠0	≠0
58 - 64	0x3a-0x40	:;<=>?@	0	≠0	0	0	≠0	≠0	0	0	0	0	0	0
65 - 70	0x41-0x46	ABCDEF	0	≠0	0	0	≠0	0	≠0	≠0	≠0	0	0	≠0
71 - 90	0x47-0x5A	GHIJKLMNOPQRSTUVWXYZ	0	≠0	0	0	≠0	0	≠0	≠0	≠0	0	0	0
91 - 96	0x5B-0x60	[\]^_`	0	≠0	0	0	≠0	≠0	0	0	0	0	0	0
97 -102	0x61-0x66	abcdef	0	≠0	0	0	≠0	0	≠0	≠0	0	≠0	0	≠0
103-122	0x67-0x7A	ghijklmnopqrstuvwxyz	0	≠0	0	0	≠0	0	≠0	≠0	0	≠0	0	0
123-126	0x7B-0x7E	{|}~	0	≠0	0	0	≠0	≠0	0	0	0	0	0	0
127	0x7F	backspace character (DEL)	≠0	0	0	0	0	0	0	0	0	0	0	0