std::toupper
<cctype>
Converts the given character to uppercase according to the character conversion rules defined by the currently installed C locale.
In the default "C" locale, the following lowercase letters abcdefghijklmnopqrstuvwxyz are replaced with respective uppercase letters ABCDEFGHIJKLMNOPQRSTUVWXYZ.
[edit] Parameters
[edit] Return value
Converted character or ch if no uppercase version is defined by the current C locale.
[edit] Notes
Like all other functions from <cctype>, the behavior of std::toupper 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:
char my_toupper(char ch) { return static_cast<char>(std::toupper(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:
std::string str_toupper(std::string s) { std::transform (s.begin(), s.end(), s.begin(), // static_cast<int(*)(int)>(std::toupper) // wrong // [](int c){ return std::toupper(c); } // wrong // [](char c){ return std::toupper(c); } // wrong [](unsigned char c){ return std::toupper(c); } // correct ); return s; }
[edit] Example
#include <cctype> #include <climits> #include <clocale> #include <iostream> #include <ranges> int main() { for (auto bd{0}; unsigned char lc : std::views::iota (0, UCHAR_MAX )) if (unsigned char uc = std::toupper(lc); uc != lc) std::cout << lc << uc << (13 == ++bd ? '\n' : ' '); std::cout << "\n\n"; unsigned char c = '\xb8'; // the character ž in ISO-8859-15 // but ̧ (cedilla) in ISO-8859-1 std::setlocale (LC_ALL, "en_US.iso88591"); std::cout << std::hex << std::showbase ; std::cout << "in iso8859-1, toupper('0xb8') gives " << std::toupper(c) << '\n'; std::setlocale (LC_ALL, "en_US.iso885915"); std::cout << "in iso8859-15, toupper('0xb8') gives " << std::toupper(c) << '\n'; }
Output:
aA bB cC dD eE fF gG hH iI jJ kK lL mM
nN oO pP qQ rR sS tT uU vV wW xX yY zZ
in iso8859-1, toupper('0xb8') gives 0xb8
in iso8859-15, toupper('0xb8') gives 0xb4