std::isalpha
Defined in header <cctype>
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int isalpha( int ch ); |
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Checks if the given character is an alphabetic character as classified by the currently installed C locale. In the default locale, the following characters are alphabetic:
- uppercase letters
ABCDEFGHIJKLMNOPQRSTUVWXYZ
- lowercase letters
abcdefghijklmnopqrstuvwxyz
In locales other than "C", an alphabetic character is a character for which std::isupper() or std::islower() returns non-zero or any other character considered alphabetic by the locale. In any case, std::iscntrl(), std::isdigit(), std::ispunct() and std::isspace() will return zero for this character.
The behavior is undefined if the value of ch
is not representable as unsigned char or is not equal to EOF.
Parameters
ch | - | character to classify |
Return value
Non-zero value if the character is an alphabetic character, zero otherwise.
Example
Demonstrates the use of isalpha() with different locales (OS-specific).
#include <iostream> #include <cctype> #include <clocale> int main() { unsigned char c = '\xdf'; // German letter ß in ISO-8859-1 std::cout << "isalpha(\'\\xdf\', default C locale) returned " << std::boolalpha << (bool)std::isalpha(c) << '\n'; std::setlocale(LC_ALL, "de_DE.iso88591"); std::cout << "isalpha(\'\\xdf\', ISO-8859-1 locale) returned " << std::boolalpha << (bool)std::isalpha(c) << '\n'; }
Output:
isalpha('\xdf', default C locale) returned false isalpha('\xdf', ISO-8859-1 locale) returned true
See also
checks if a character is classified as alphabetic by a locale (function template) | |
checks if a wide character is alphabetic (function) | |
C documentation for isalpha
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ASCII values (hex) |
characters |
isalpha |
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0 - 8 | 0x00-0x08
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control codes (NUL , etc.)
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≠0
|
0
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0
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0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
9 | 0x09
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tab (\t )
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≠0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
10 - 13 | 0x0A-0x0D
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whitespaces (\n ,\v ,\f ,\r )
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≠0
|
0
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≠0
|
0
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0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
14 - 31 | 0x0E-0x1F
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control codes | ≠0
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0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
32 | 0x20
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space | 0
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≠0
|
≠0
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≠0
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0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
33 - 47 | 0x21-0x2F
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!"#$%&'()*+,-./
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0
|
≠0
|
0
|
0
|
≠0
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≠0
|
0
|
0
|
0
|
0
|
0
|
0
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48 - 57 | 0x30-0x39
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0123456789
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0
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≠0
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0
|
0
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≠0
|
0
|
≠0
|
0
|
0
|
0
|
≠0
|
≠0
|
58 - 64 | 0x3a-0x40
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:;<=>?@
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0
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≠0
|
0
|
0
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≠0
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≠0
|
0
|
0
|
0
|
0
|
0
|
0
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65 - 70 | 0x41-0x46
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ABCDEF
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0
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≠0
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0
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0
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≠0
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0
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≠0
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≠0
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≠0
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0
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0
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≠0
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71 - 90 | 0x47-0x5A
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GHIJKLMNOPQRSTUVWXYZ
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0
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≠0
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0
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0
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≠0
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0
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≠0
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≠0
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≠0
|
0
|
0
|
0
|
91 - 96 | 0x5B-0x60
|
[\]^_`
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0
|
≠0
|
0
|
0
|
≠0
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≠0
|
0
|
0
|
0
|
0
|
0
|
0
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97 -102 | 0x61-0x66
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abcdef
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0
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≠0
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0
|
0
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≠0
|
0
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≠0
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≠0
|
0
|
≠0
|
0
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≠0
|
103-122 | 0x67-0x7A
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ghijklmnopqrstuvwxyz
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0
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≠0
|
0
|
0
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≠0
|
0
|
≠0
|
≠0
|
0
|
≠0
|
0
|
0
|
123-126 | 0x7B-0x7E
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{|}~
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0
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≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
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127 | 0x7F
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backspace character (DEL )
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≠0
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0
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0
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0
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0
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0
|
0
|
0
|
0
|
0
|
0
|
0
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