std::ctype::tolower, std::ctype::do_tolower

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

 

std::ctype

Member functions

ctype::ctype

ctype::~ctype

ctype::isctype::do_is

ctype::scan_isctype::do_scan_is

ctype::scan_notctype::do_scan_not

ctype::toupperctype::do_toupper

ctype::tolowerctype::do_tolower

ctype::widenctype::do_widen

ctype::narrowctype::do_narrow

Member functions of ctype<char>

ctype<char>::ctype

ctype<char>::~ctype

ctype<char>::table

ctype<char>::classic_table

ctype<char>::is

ctype<char>::scan_is

ctype<char>::scan_not

 

Defined in header <locale>
public: CharT tolower( CharT c ) const;	(1)
public: const CharT* tolower( CharT* beg, const CharT* end ) const;	(2)
protected: virtual CharT do_tolower( CharT c ) const;	(3)
protected: virtual const CharT* do_tolower( CharT* beg, const CharT* end ) const;	(4)

1,2) public member function, calls the protected virtual member function do_tolower of the most derived class.

3) Converts the character c to lower case if a lower case form is defined by this locale.

4) For every character in the character array [beg, end), for which a lower case form exists, replaces the character with that lower case form.

Parameters

c	-	character to convert
beg	-	pointer to the first character in an array of characters to convert
end	-	one past the end pointer for the array of characters to convert

Return value

1,3) lower case character or c if no lower case form is listed by this locale.

2,4) end.

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 do_tolower cannot be used to obtain the correct lowercase form in this case.

Example

Run this code

#include <locale>
#include <iostream>
 
void try_lower(const std::ctype<wchar_t>& f, wchar_t c)
{
    wchar_t up = f.tolower(c);
    if (up != c) {
        std::wcout << "Lower case form of \'" << c << "' is " << up << '\n';
    } else {
        std::wcout << '\'' << c << "' has no lower case form\n";
    }
}
 
int main()
{
    std::locale::global(std::locale("en_US.utf8"));
    std::wcout.imbue(std::locale());
    std::wcout << "In US English UTF-8 locale:\n";
    auto& f = std::use_facet<std::ctype<wchar_t>>(std::locale());
    try_lower(f, L'Σ');
    try_lower(f, L'Ɛ');
    try_lower(f, L'Ａ');
 
    std::wstring str = L"HELLo, wORLD!";
    std::wcout << "Lowercase form of the string '" << str << "' is ";
    f.tolower(&str[0], &str[0] + str.size());
    std::wcout << "'" << str << "'\n";
}

Output:

In US English UTF-8 locale:
Lower case form of 'Σ' is σ
Lower case form of 'Ɛ' is ɛ
Lower case form of 'Ａ' is ａ
Lowercase form of the string 'HELLo, wORLD!' is 'hello, world!'

See also

toupper	invokes do_toupper (public member function)
tolower	converts a character to lowercase (function)
towlower	converts a wide character to lowercase (function)