std::isupper

From cppreference.com
< cpp‎ | string‎ | byte
Defined in header <cctype>
int isupper( int ch );

Checks if the given character is an uppercase character as classified by the currently installed C locale. In the default "C" locale, isupper returns a nonzero value only for the uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ).

If isupper returns a nonzero value, it is guaranteed that iscntrl, isdigit, ispunct, and isspace return zero for the same character in the same C locale.

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 uppercase letter, zero otherwise.

Notes

Like all other functions from <cctype>, the behavior of std::isupper 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_isupper(char ch)
{
    return std::isupper(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_uppers(const std::string& s)
{
    return std::count_if(s.begin(), s.end(), 
                      // static_cast<int(*)(int)>(std::isupper)         // wrong
                      // [](int c){ return std::isupper(c); }           // wrong
                      // [](char c){ return std::isupper(c); }          // wrong
                         [](unsigned char c){ return std::isupper(c); } // correct
                        );
}

Example

#include <iostream>
#include <cctype>
#include <clocale>
 
int main()
{
    unsigned char c = '\xc6'; // letter Æ in ISO-8859-1
 
    std::cout << "isupper(\'\\xc6\', default C locale) returned "
               << std::boolalpha << (bool)std::isupper(c) << '\n';
 
    std::setlocale(LC_ALL, "en_GB.iso88591");
    std::cout << "isupper(\'\\xc6\', ISO-8859-1 locale) returned "
              << std::boolalpha << (bool)std::isupper(c) << '\n';
 
}

Output:

isupper('\xc6', default C locale) returned false
isupper('\xc6', ISO-8859-1 locale) returned true


See also

checks if a character is classified as uppercase by a locale
(function template)
checks if a wide character is an uppercase character
(function)
ASCII values 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

decimal hexadecimal octal
0–8 \x0\x8 \0\10 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0
9 \x9 \11 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
10–13 \xA\xD \12\15 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
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 :;<=>[email protected] 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
QRSTUVWXYZ
0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
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
qrstuvwxyz
0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
123–126 \x7B\x7E \172\176 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
127 \x7F \177 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0