NAME¶

std::tolower(std::locale) - std::tolower(std::locale)

Synopsis¶

Defined in header <locale>
template< class CharT >
CharT tolower( CharT ch, const locale& loc );

Converts the character ch to lowercase if possible, using the conversion rules
specified by the given locale's std::ctype facet.

Parameters¶

ch - character
loc - locale

Return value¶

Returns the lowercase form of ch if one is listed in the locale, otherwise return ch
unchanged.

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 std::tolower cannot be used to obtain the correct lowercase
form in this case.

Possible implementation¶

template<class CharT>
CharT tolower(CharT ch, const std::locale& loc)
{
return std::use_facet<std::ctype<CharT>>(loc).tolower(ch);
}

Example¶

// Run this code

#include <cwctype>
#include <iostream>
#include <locale>

int main()
{
wchar_t c = L'\u0190'; // Latin capital open E ('Ɛ')

std::cout << std::hex << std::showbase;

std::cout << "in the default locale, tolower(" << (std::wint_t)c << ") = "
<< (std::wint_t)std::tolower(c, std::locale()) << '\n';

std::cout << "in Unicode locale, tolower(" << (std::wint_t)c << ") = "
<< (std::wint_t)std::tolower(c, std::locale("en_US.utf8")) << '\n';
}

Possible output:¶

in the default locale, tolower(0x190) = 0x190
in Unicode locale, tolower(0x190) = 0x25b

See also¶

converts a character to uppercase using the ctype facet of a
toupper(std::locale) locale
(function template)
tolower converts a character to lowercase
(function)
towlower converts a wide character to lowercase
(function)