Difference between revisions of "cpp/string/wide/towlower"
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===Notes=== | ===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 {{ | + | Only 1:1 character mapping can be performed by this function, e.g. the Greek uppercase letter {{c/core|'Σ'}} has two lowercase forms, depending on the position in a word: {{c/core|'σ'}} and {{c/core|'ς'}}. A call to {{tt|std::towlower}} cannot be used to obtain the correct lowercase form in this case. |
| − | [ | + | [https://www.open-std.org/JTC1/SC35/WG5/docs/30112d10.pdf ISO 30112] specifies which pairs of Unicode characters are included in this mapping. |
===Example=== | ===Example=== | ||
| Line 33: | Line 33: | ||
std::cout << std::hex << std::showbase; | std::cout << std::hex << std::showbase; | ||
| − | std::cout << "in the default locale, towlower(" << | + | std::cout << "in the default locale, towlower(" |
| + | << static_cast<std::wint_t>(c) << ") = " | ||
<< std::towlower(c) << '\n'; | << std::towlower(c) << '\n'; | ||
std::setlocale(LC_ALL, "en_US.utf8"); | std::setlocale(LC_ALL, "en_US.utf8"); | ||
| − | std::cout << "in Unicode locale, towlower(" << | + | std::cout << "in Unicode locale, towlower(" |
| + | << static_cast<std::wint_t>(c) << ") = " | ||
<< std::towlower(c) << '\n'; | << std::towlower(c) << '\n'; | ||
} | } | ||
Latest revision as of 09:27, 15 September 2023
| Defined in header <cwctype>
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| std::wint_t towlower( std::wint_t ch ); |
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Converts the given wide character to lowercase, if possible.
If the value of ch is neither representable as a wchar_t nor equal to the value of the macro WEOF, the behavior is undefined.
Contents |
[edit] Parameters
| ch | - | wide character to be converted |
[edit] Return value
Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale.
[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::towlower cannot be used to obtain the correct lowercase form in this case.
ISO 30112 specifies which pairs of Unicode characters are included in this mapping.
[edit] Example
Run this code
#include <clocale> #include <cwctype> #include <iostream> int main() { wchar_t c = L'\u0190'; // Latin capital open E ('Ɛ') std::cout << std::hex << std::showbase; std::cout << "in the default locale, towlower(" << static_cast<std::wint_t>(c) << ") = " << std::towlower(c) << '\n'; std::setlocale(LC_ALL, "en_US.utf8"); std::cout << "in Unicode locale, towlower(" << static_cast<std::wint_t>(c) << ") = " << std::towlower(c) << '\n'; }
Output:
in the default locale, towlower(0x190) = 0x190 in Unicode locale, towlower(0x190) = 0x25b
[edit] See also
| converts a wide character to uppercase (function) | |
converts a character to lowercase using the ctype facet of a locale (function template) | |
| converts a character to lowercase (function) | |
| C documentation for towlower
| |
