std::is_copy_constructible, std::is_trivially_copy_constructible, std::is_nothrow_copy_constructible

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C++
 
實用工具庫
類型的支持 (basic types, RTTI, type traits)
動態內存管理
錯誤處理
程序實用工具
可變參數函數
日期和時間
函數對象
initializer_list（C++11）
bitset
hash（C++11）
關係運算符
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Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
雙和元組
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Pairs and tuples
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pair
tuple（C++11）
piecewise_construct_t（C++11）
piecewise_construct（C++11）
掉期，遠期和移動
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Swap, forward and move
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swap
forward（C++11）
move（C++11）
move_if_noexcept（C++11）
declval（C++11）
 
類型的支持
基本類型
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Basic types
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基本類型
固定寬度的整數類型 （C++11）
nullptr_t（C++11）
offsetof
NULL
數值範圍內
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Numeric limits
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numeric_limits
C數字限制介面
運行時類型信息
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Runtime type information
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type_info
type_index（C++11）
類型特徵
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Type traits
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初級型兩類
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Primary type categories
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is_void（C++11）
is_array（C++11）
is_pointer（C++11）
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is_class（C++11）
is_function（C++11）
is_object（C++11）
is_scalar（C++11）
is_compound（C++11）
is_integral（C++11）
is_floating_point（C++11）
is_fundamental（C++11）
is_arithmetic（C++11）
is_reference（C++11）
is_lvalue_reference（C++11）
is_rvalue_reference（C++11）
is_member_pointer（C++11）
is_member_object_pointer（C++11）
is_member_function_pointer（C++11）
類型屬性
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Type properties
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is_const（C++11）
is_volatile（C++11）
is_pod（C++11）
is_empty（C++11）
is_polymorphic（C++11）
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is_trivial（C++11）
is_trivially_copyable（C++11）
is_standard_layout（C++11）
is_literal_type（C++11）
is_signed（C++11）
is_unsigned（C++11）
支持的操作
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Supported operations
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is_constructible
is_trivially_constructible
is_nothrow_constructible		（C++11）
（C++11）
（C++11）
is_default_constructible
is_trivially_default_constructible
is_nothrow_default_constructible		（C++11）
（C++11）
（C++11）
is_copy_constructible
is_trivially_copy_constructible
is_nothrow_copy_constructible		（C++11）
（C++11）
（C++11）
is_move_constructible
is_trivially_move_constructible
is_nothrow_move_constructible		（C++11）
（C++11）
（C++11）
is_assignable
is_trivially_assignable
is_nothrow_assignable		（C++11）
（C++11）
（C++11）
is_copy_assignable
is_trivially_copy_assignable
is_nothrow_copy_assignable		（C++11）
（C++11）
（C++11）
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable		（C++11）
（C++11）
（C++11）
is_destructible
is_trivially_destructible
is_nothrow_destructible		（C++11）
（C++11）
（C++11）
has_virtual_destructor（C++11）
關係和屬性查詢
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Relationships and property queries
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is_same（C++11）
is_base_of（C++11）
is_convertible（C++11）
alignment_of（C++11）
rank（C++11）
extent（C++11）
類型的修改
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Type modifications
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remove_cv
remove_const
remove_volatile		（C++11）
（C++11）
（C++11）
add_cv
add_const
add_volatile		（C++11）
（C++11）
（C++11）
make_signed（C++11）
make_unsigned（C++11）
remove_reference（C++11）
add_lvalue_reference
add_rvalue_reference		（C++11）
（C++11）
remove_pointer（C++11）
add_pointer（C++11）
remove_extent（C++11）
remove_all_extents（C++11）
類型轉換
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Type transformations
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aligned_storage（C++11）
aligned_union（C++11）
decay（C++11）
enable_if（C++11）
conditional（C++11）
common_type（C++11）
underlying_type（C++11）
result_of（C++11）
鍵入特徵常數
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Type trait constants
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integral_constant（C++11）
 
Defined in header <type_traits>
template< class T >
struct is_copy_constructible;
 (1) （C++11 起）
template< class T >
struct is_trivially_copy_constructible;
 (2) （C++11 起）
template< class T >
struct is_nothrow_copy_constructible;
 (3) （C++11 起）
1)
檢查一個類型是否是CopyConstructible，即具有可訪問的顯式或隱式的拷貝構造函數。如果符合要求，一個成員value等於true，否則value是false.
Original:
Checks whether a type is CopyConstructible, i.e. has an accessible explicit or implicit copy constructor. If the requirement is met, a member constant value equal true is provided, otherwise value is false.
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2)
同（1），但拷貝構造函數的表達不調用任何操作，是不平凡的.
Original:
Same as (1), but the copy constructor expression does not call any operation that is not trivial.
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3)
同（1），但拷貝構造函數的表達noexcept.
Original:
Same as (1), but the copy constructor expression is noexcept.
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目錄

Inherited from std::integral_constant

Member constants

value
[靜態的] </ SPAN></div></div>
true如果 T is copy-constructible ，false其他方式
Original:
true if T is copy-constructible , false otherwise
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（公共靜態成員常量）

Member functions

operator bool
轉換的對象bool，返回value
Original:
converts the object to bool, returns value
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（公共成員函數）

Member types

類型
Original:
Type
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 Definition
value_type bool
type std::integral_constant<bool, value>

</div>

[编辑] 可能的實現

template<class T>
struct is_copy_constructible :
    std::is_constructible<T, const typename std::add_lvalue_reference<T>::type> {};
 
template<class T>
struct is_trivially_copy_constructible :
    std::is_trivially_constructible<T, const typename std::add_lvalue_reference<T>::type> {};
 
template<class T>
struct is_nothrow_copy_constructible :
    std::is_nothrow_constructible<T, const typename std::add_lvalue_reference<T>::type> {};

[编辑] 為例

#include <iostream>
#include <type_traits>
 
struct Ex1 {
    std::string str; // member has a non-trivial copy ctor
};
struct Ex2 {
    int n;
    Ex2(const Ex2&) = default; // trivial and non-throwing
};
 
int main() {
    std::cout << std::boolalpha << "Ex1 is copy-constructible? "
              << std::is_copy_constructible<Ex1>::value << '\n'
              << "Ex1 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex1>::value << '\n'
              << "Ex2 is trivially copy-constructible? "
              << std::is_trivially_copy_constructible<Ex2>::value << '\n'
              << "Ex2 is nothrow copy-constructible? "
              << std::is_nothrow_copy_constructible<Ex2>::value << '\n';
}

Output: 

Ex1 is copy-constructible? true
Ex1 is trivially copy-constructible? false
Ex2 is trivially copy-constructible? true
Ex2 is nothrow copy-constructible? true

[编辑] 另請參閱

（C++11）
（C++11）
（C++11）
檢查如果一個類型有一個構造函數的具體參數
Original:
checks if a type has a constructor for specific arguments
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（類模板） [edit]
（C++11）
（C++11）
（C++11）
檢查如果一個類型有一個默認的構造函數
Original:
checks if a type has a default constructor
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（類模板） [edit]
（C++11）
（C++11）
（C++11）
類型檢查，如果有一個移動的構造函數
Original:
checks if a type has a move constructor
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（類模板） [edit]
来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/types/is_copy_constructible&oldid=27505”