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std::tolower(std::locale)

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Revision as of 08:14, 18 September 2013 by Cubbi (Talk | contribs)

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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.

Contents

[edit] Parameters

ch - character
loc - locale

[edit] Return value

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

[edit] 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.

[edit] Possible implementation

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

[edit] Example

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

Output:

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

[edit] See also

converts a character to uppercase using the ctype facet of a locale
(function template) [edit]
converts a character to lowercase
(function) [edit]
converts a wide character to lowercase
(function) [edit]