std::remove_cv, std::remove_const, std::remove_volatile

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C++
 
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remove_cv
remove_const
remove_volatile		（C++11）
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Defined in header <type_traits>
template< class T >
struct remove_cv;
 (1) （C++11 起）
template< class T >
struct remove_const;
 (2) （C++11 起）
template< class T >
struct remove_volatile;
 (3) （C++11 起）

Provides the member typedef type which is the same as T, except that its topmost cv-qualifiers are removed.

1) removes the topmost const, the topmost volatile, or both, if present.

2) removes the topmost const

3) removes the topmost volatile

目录

[编辑] 会员类型

姓名
Original:
Name
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 Definition
type the type T without cv-qualifier

[编辑] 可能的实现

template< class T >
struct remove_cv {
    typedef typename std::remove_volatile<typename std::remove_const<T>::type>::type type;
};
 
template< class T > struct remove_const          { typedef T type; };
template< class T > struct remove_const<const T> { typedef T type; };
 
template< class T > struct remove_volatile             { typedef T type; };
template< class T > struct remove_volatile<volatile T> { typedef T type; };

[编辑] 为例

Removing const/volatile from const volatile int * does not modify the type, because the pointer itself is neither const nor volatile. 

#include <iostream>
#include <type_traits>
 
int main() {
    typedef std::remove_cv<const int>::type type1;
    typedef std::remove_cv<volatile int>::type type2;
    typedef std::remove_cv<const volatile int>::type type3;
    typedef std::remove_cv<const volatile int*>::type type4;
    typedef std::remove_cv<int * const volatile>::type type5;
 
    std::cout << "test1 " << (std::is_same<int, type1>::value
        ? "passed" : "failed") << '\n';
    std::cout << "test2 " << (std::is_same<int, type2>::value
        ? "passed" : "failed") << '\n';
    std::cout << "test3 " << (std::is_same<int, type3>::value
        ? "passed" : "failed") << '\n';
    std::cout << "test4 " << (std::is_same<const volatile int*, type4>::value
        ? "passed" : "failed") << '\n';
    std::cout << "test5 " << (std::is_same<int*, type5>::value
        ? "passed" : "failed") << '\n';
}

Output: 

test1 passed
test2 passed
test3 passed
test4 passed
test5 passed

[编辑] 另请参阅

（C++11）
检查如果一个类型是const限定
Original:
checks if a type is const-qualified
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（类模板） [edit]
（C++11）
类型检查，如果是挥发合格的
Original:
checks if a type is volatile-qualified
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（类模板） [edit]
来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/types/remove_cv&oldid=26798”