std::isxdigit(3)

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 an hexadecimal numeric character, zero otherwise.

Notes
   isdigit and 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
                        );
 }

See also
                        checks if a character is classified as a hexadecimal digit by
   isxdigit(std::locale) a locale
                        (function template)
   iswxdigit checks if a character is a hexadecimal character
                        (function)
          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 0â€“8 \x0â€“\x8 \0â€“\10 control codes â‰ 0 0 0 0 0 0 0 0 0 0 0 0
                        (NUL, etc.) 9 \x9 \11 tab (\t) â‰ 0 0 â‰ 0 â‰ 0 0 0 0 0 0 0 0 0
                        whitespaces 10â€“13 \xAâ€“\xD \12â€“\15 (\n, \v, \f, â‰ 0 0 â‰ 0 0 0 0 0 0 0 0 0 0
                        \r) 14â€“31 \xEâ€“\x1F \16â€“\37 control codes â‰ 0 0 0 0 0 0 0 0 0 0 0 0 32 \x20 \40 space 0 â‰ 0 â‰ 0 â‰ 0 0 0 0 0 0 0 0 0 33â€“47 \x21â€“\x2F \41â€“\57 !"#$%&'()*+,-./ 0 â‰ 0 0 0 â‰ 0 â‰ 0 0 0 0 0 0 0 48â€“57 \x30â€“\x39 \60â€“\71 0123456789 0 â‰ 0 0 0 â‰ 0 0 â‰ 0 0 0 0 â‰ 0 â‰ 0 58â€“64 \x3Aâ€“\x40 \72â€“\100 :;<=>?@ 0 â‰ 0 0 0 â‰ 0 â‰ 0 0 0 0 0 0 0 65â€“70 \x41â€“\x46 \101â€“\106 ABCDEF 0 â‰ 0 0 0 â‰ 0 0 â‰ 0 â‰ 0 â‰ 0 0 0 â‰ 0 71â€“90 \x47â€“\x5A \107â€“\132 GHIJKLMNOP 0 â‰ 0 0 0 â‰ 0 0 â‰ 0 â‰ 0 â‰ 0 0 0 0
                        QRSTUVWXYZ 91â€“96 \x5Bâ€“\x60 \133â€“\140 [\]^_` 0 â‰ 0 0 0 â‰ 0 â‰ 0 0 0 0 0 0 0 97â€“102 \x61â€“\x66 \141â€“\146 abcdef 0 â‰ 0 0 0 â‰ 0 0 â‰ 0 â‰ 0 0 â‰ 0 0 â‰ 0 103â€“122 \x67â€“\x7A \147â€“\172 ghijklmnop 0 â‰ 0 0 0 â‰ 0 0 â‰ 0 â‰ 0 0 â‰ 0 0 0
                        qrstuvwxyz 123â€“126 \x7Bâ€“\x7E \172â€“\176 {|}~ 0 â‰ 0 0 0 â‰ 0 â‰ 0 0 0 0 0 0 0 127 \x7F \177 backspace â‰ 0 0 0 0 0 0 0 0 0 0 0 0
                        character (DEL)