remove_extent

#include <iostream>
#include <memory>
#include <type_traits>
#include <typeinfo>

template<class T>
struct remove_extent { typedef T type; };
 
template<class T>
struct remove_extent<T[]> { typedef T type; };
 
template<class T, std::size_t N>
struct remove_extent<T[N]> { typedef T type; };

int main()
{
    std::cout << typeid(remove_extent<int>::type).name() << std::endl;
    std::cout << typeid(remove_extent<int[]>::type).name() << std::endl;
    std::cout << typeid(remove_extent<int[5]>::type).name() << std::endl;
    return 0;
}

输出结果为：

:g++ -std=c++11 main.cc -o main
:./main | c++filt
int
int
int

std::is_array

#include <iostream>
#include <memory>
#include <type_traits>
#include <typeinfo>

template<class T>
struct is_array : std::false_type {};
 
template<class T>
struct is_array<T[]> : std::true_type {};
 
template<class T, std::size_t N>
struct is_array<T[N]> : std::true_type {};

int main()
{
    using int_array_type = int[5];
    std::cout << is_array<int>::value << std::endl;
    std::cout << is_array<int[]>::value << std::endl;
    std::cout << is_array<int[5]>::value << std::endl;
    std::cout << is_array<int_array_type>::value << std::endl;
    return 0;
}

输出结果为：

:g++ -std=c++11 main.cc -o main
:./main | c++filt
0
1
1
1

std::rank

#include <iostream>
#include <memory>
#include <type_traits>
#include <typeinfo>

template<class T>
struct rank : public std::integral_constant<std::size_t, 0> {};
 
template<class T>
struct rank<T[]> : public std::integral_constant<std::size_t, rank<T>::value + 1> {};
 
template<class T, std::size_t N>
struct rank<T[N]> : public std::integral_constant<std::size_t, rank<T>::value + 1> {};

int main()
{
    using int_array_type = int[5];
    std::cout << rank<int>::value << std::endl;
    std::cout << rank<int[]>::value << std::endl;
    std::cout << rank<int[5]>::value << std::endl;
    std::cout << rank<int_array_type>::value << std::endl;
    std::cout << rank<int_array_type[]>::value << std::endl;
    std::cout << rank<int_array_type[5]>::value << std::endl;
    return 0;
}

输出结果为：

:g++ -std=c++11 -O0 main.cc -o main
:./main
0
1
1
1
2
2

std::remove_all_extents

#include <iostream>
#include <memory>
#include <type_traits>
#include <typeinfo>

template<class T>
struct remove_all_extents { typedef T type;};
 
template<class T>
struct remove_all_extents<T[]> {
    typedef typename remove_all_extents<T>::type type;
};
 
template<class T, std::size_t N>
struct remove_all_extents<T[N]> {
    typedef typename remove_all_extents<T>::type type;
};

int main()
{
    using int_array_type = int[5];
    std::cout << typeid(remove_all_extents<int>::type).name() << std::endl;
    std::cout << typeid(remove_all_extents<int[]>::type).name() << std::endl;
    std::cout << typeid(remove_all_extents<int[5]>::type).name() << std::endl;
    std::cout << typeid(remove_all_extents<int_array_type>::type).name() << std::endl;
    std::cout << typeid(remove_all_extents<int_array_type[]>::type).name() << std::endl;
    std::cout << typeid(remove_all_extents<int_array_type[5]>::type).name() << std::endl;
    return 0;
}

输出结果为：

:g++ -std=c++11 -O0 main.cc -o main
:./main | c++filt
int
int
int
int
int
int