std::ctype::do_tolower

STD：：Ctype：：Tolower，STD：：Ctype：：do[医]收费人

Defined in header
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%29的公共成员函数，调用受保护的虚拟成员函数。do_tolower最派生的类。

3%29转换字符c如果此区域设置定义了小写窗体，则为小写。

4%29对字符数组中的每个字符[beg, end)，如果存在小写窗体，则将字符替换为该小写窗体。

参数

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

返回值

1，3%29小写字符或c如果此区域设置没有列出小写窗体。

2，4%29end...

注记

这个函数只能执行01：1的字符映射，例如，希腊大写字母%27Σ%27有两个小写形式，取决于单词中的位置：%27σ%27和%27%100。打电话给do_tolower在这种情况下，无法使用它获得正确的小写形式。

例

二次

#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";
}

二次

产出：

二次

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!'

二次

另见

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

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