std::ctype<CharT>::tolower, std::ctype<CharT>::do_tolower
定义于头文件 <locale>
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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) 公开成员函数,调用最终导出类上的受保护虚成员函数
do_tolower
。3) 若此 locale 定义
c
的小写形式,则转换它为小写形式。4) 对字符数组
[beg, end)
中每个存在小写形式的字符,以其小写形式替换该字符。参数
c | - | 要转换的字符 |
beg | - | 指向要转换的数组中首字符的指针 |
end | - | 指向要转换的数组尾后一位置的指针 |
返回值
1,3) 小写字符,或若无列于此 loacale 的小写形式则为
c
。2,4)
end
。注意
此函数只能进行 1:1 字符映射,例如希腊文大写字母 'Σ' 拥有二个小写形式,取决于在词中的位置: 'σ' 与 'ς' 。此情况下对 do_tolower
的调用不能获得正确的小写形式。
示例
运行此代码
#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"; }
输出:
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!'
参阅
调用 do_toupper (公开成员函数) | |
转换字符为小写 (函数) | |
转换宽字符为小写 (函数) |