NAME¶

std::isxdigit - std::isxdigit

Synopsis¶

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

Checks if the given character is a hexadecimal numeric character
(0123456789abcdefABCDEF).

The behavior is undefined if the value of ch is not representable as unsigned char
and is not equal to EOF.

Parameters¶

ch - character to classify

Return value¶

Non-zero value if the character is a hexadecimal numeric character, zero otherwise.

Notes¶

std::isdigit and std::isxdigit are the only standard narrow character classification
functions that are not affected by the currently installed C locale. although some
implementations (e.g. Microsoft in 1252 codepage) may classify additional
single-byte characters as digits.

Like all other functions from <cctype>, the behavior of std::isxdigit is undefined
if the argument's value is neither representable as unsigned char nor equal to EOF.
To use these functions safely with plain chars (or signed chars), the argument
should first be converted to unsigned char:

bool my_isxdigit(char ch)
{
return std::isxdigit(static_cast<unsigned char>(ch));
}

Similarly, they should not be directly used with standard algorithms when the
iterator's value type is char or signed char. Instead, convert the value to unsigned
char first:

int count_xdigits(const std::string& s)
{
return std::count_if(s.begin(), s.end(),
// static_cast<int(*)(int)>(std::isxdigit) // wrong
// [](int c){ return std::isxdigit(c); } // wrong
// [](char c){ return std::isxdigit(c); } // wrong
[](unsigned char c){ return std::isxdigit(c); } // correct
);
}

Example¶

// Run this code

#include <cctype>
#include <climits>
#include <iostream>

int main()
{
for (int c = 0; UCHAR_MAX >= c; ++c)
if (isxdigit(c))
std::cout << static_cast<char>(c);
std::cout << '\n';
}

Output:¶

0123456789ABCDEFabcdef

See also¶

checks if a character is classified as a hexadecimal digit by
isxdigit(std::locale) a locale
(function template)
iswxdigit checks if a wide character is a hexadecimal character
(function)
C documentation for
isxdigit

ASCII values characters iscntrl isprint isspace isblank isgraph ispunct isalnum isalpha isupper islower isdigit isxdigit decimal hexadecimal octal iswcntrl iswprint iswspace iswblank iswgraph iswpunct iswalnum iswalpha iswupper iswlower iswdigit iswxdigit 0–8 \x0–\x8 \0–\10 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0
(NUL, etc.) 9 \x9 \11 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
whitespaces 10–13 \xA–\xD \12–\15 (\n, \v, \f, ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
\r) 14–31 \xE–\x1F \16–\37 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0 32 \x20 \40 space 0 ≠0 ≠0 ≠0 0 0 0 0 0 0 0 0 33–47 \x21–\x2F \41–\57 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 48–57 \x30–\x39 \60–\71 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0 58–64 \x3A–\x40 \72–\100 :;<=>?@ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 65–70 \x41–\x46 \101–\106 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0 71–90 \x47–\x5A \107–\132 GHIJKLMNOP 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
QRSTUVWXYZ 91–96 \x5B–\x60 \133–\140 [\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 97–102 \x61–\x66 \141–\146 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0 103–122 \x67–\x7A \147–\172 ghijklmnop 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
qrstuvwxyz 123–126 \x7B–\x7E \172–\176 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 127 \x7F \177 backspace ≠0 0 0 0 0 0 0 0 0 0 0 0
character (DEL)