std::tolower(std::locale) - cppreference.com

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# std::tolower(std::locale)

From cppreference.com
< cpp‎ | locale

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.

### [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

Run this code

    #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

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

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