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Difference between revisions of "cpp/string/wide/towlower"

From cppreference.com
< cpp‎ | string‎ | wide
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{{cpp/title|towlower}}
 
{{cpp/title|towlower}}
 
{{cpp/string/wide/navbar}}
 
{{cpp/string/wide/navbar}}
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{{ddcl | header=cwctype |
+
{{ddcl|header=cwctype|
−
wint_t towlower( wint_t ch );
+
std::wint_t towlower( std::wint_t ch );
 
}}
 
}}
 
Converts the given wide character to lowercase, if possible.
 
Converts the given wide character to lowercase, if possible.
 +
 +
{{cpp/string/wide/wint_t args}}
  
 
===Parameters===
 
===Parameters===
−
{{param list begin}}
+
{{par begin}}
−
{{param list item | ch | wide character to be converted}}
+
{{par|ch|wide character to be converted}}
−
{{param list end}}
+
{{par end}}
  
 
===Return value===
 
===Return value===
−
Lowercase version of {{tt|ch}} or unmodified {{tt|ch}} if no lowercase version is listed in the current C locale.
+
Lowercase version of {{c|ch}} or unmodified {{c|ch}} if no lowercase version is listed in the current C locale.
  
 
===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 {{c|std::towlower}} cannot be used to obtain the correct lowercase form in this case.  
+
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
 +
|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
 +
}}
  
 
===See also===
 
===See also===
−
{{dcl list begin}}
+
{{dsc begin}}
−
{{dcl list template | cpp/string/wide/dcl list towupper}}
+
{{dsc inc|cpp/string/wide/dsc towupper}}
−
{{dcl list template | cpp/locale/dcl list tolower}}
+
{{dsc inc|cpp/locale/dsc tolower}}
−
{{dcl list template | cpp/string/byte/dcl list tolower}}
+
{{dsc inc|cpp/string/byte/dsc tolower}}
−
{{dcl list see c | c/string/wide/towlower}}
+
{{dsc see c|c/string/wide/towlower}}
−
{{dcl list end}}
+
{{dsc end}}
 +
 
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 09:27, 15 September 2023

 
C++
 
Strings library
 
Null-terminated wide strings
 
Defined in header <cwctype>
std::wint_t towlower( std::wint_t ch );

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) [edit]
converts a character to lowercase using the ctype facet of a locale
(function template) [edit]
converts a character to lowercase
(function) [edit]
C documentation for towlower
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