NAME

std::ctype::tolower,std::ctype::do_tolower - std::ctype::tolower,std::ctype::do_tolower

Synopsis

Defined in header <locale>
public: (1)
CharT tolower( CharT c ) const;
public: (2)
const CharT* tolower( CharT* beg, const CharT* end ) const;
protected: (3)
virtual CharT do_tolower( CharT c ) const;
protected: (4)
virtual const CharT* do_tolower( CharT* beg, const CharT* end ) const;

1,2) public member function, calls the protected virtual member function do_tolower
of the most derived class.
3) Converts the character c to lower case if a lower case form is defined by this
locale.
4) For every character in the character array [beg, end), for which a lower case
form exists, replaces the character with that lower case form.

Parameters

c - character to convert
beg - pointer to the first character in an array of characters to convert
end - one past the end pointer for the array of characters to convert

Return value

1,3) lower case character or c if no lower case form is listed by this locale.
2,4) end.

Notes

Only 1:1 character mapping can be performed by this function, e.g. the Greek
uppercase letter 'Σ' has two lowercase forms, depending on the position in a word:
'σ' and 'ς'. A call to do_tolower cannot be used to obtain the correct lowercase
form in this case.

Example

// Run this code

#include <locale>
#include <iostream>

void try_lower(const std::ctype<wchar_t>& f, wchar_t c)
{
wchar_t up = f.tolower(c);
if (up != c) {
std::wcout << "Lower case form of \'" << c << "' is " << up << '\n';
} else {
std::wcout << '\'' << c << "' has no lower case form\n";
}
}

int main()
{
std::locale::global(std::locale("en_US.utf8"));
std::wcout.imbue(std::locale());
std::wcout << "In US English UTF-8 locale:\n";
auto& f = std::use_facet<std::ctype<wchar_t>>(std::locale());
try_lower(f, L'Σ');
try_lower(f, L'Ɛ');
try_lower(f, L'Ａ');

std::wstring str = L"HELLo, wORLD!";
std::wcout << "Lowercase form of the string '" << str << "' is ";
f.tolower(&str[0], &str[0] + str.size());
std::wcout << "'" << str << "'\n";
}

Output:

In US English UTF-8 locale:
Lower case form of 'Σ' is σ
Lower case form of 'Ɛ' is ɛ
Lower case form of 'Ａ' is ａ
Lowercase form of the string 'HELLo, wORLD!' is 'hello, world!'