std::remove_all_extents

 

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型別類別 is_void (C++11) is_null_pointer (C++11)(DR*) is_array (C++11) is_pointer (C++11) is_enum (C++11) is_union (C++11) is_class (C++11) is_function (C++11) is_reference (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_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) 型別屬性 is_const (C++11) is_volatile (C++11) is_empty (C++11) is_polymorphic (C++11) is_final (C++14) is_abstract (C++11) is_aggregate (C++17) is_implicit_lifetime (C++23) is_trivial (C++11)(C++26 中已棄用) is_trivially_copyable (C++11) is_standard_layout (C++11) is_literal_type (C++11)(直到 C++20*) is_pod (C++11)(C++20 中已棄用) is_signed (C++11) is_unsigned (C++11) is_bounded_array (C++20) is_unbounded_array (C++20) is_scoped_enum (C++23) has_unique_object_representations (C++17) 型別特性常量 integral_constantbool_constanttrue_typefalse_type (C++11)(C++17)(C++11)(C++11) 元函式 conjunction (C++17) disjunction (C++17) negation (C++17)	支援的操作 is_constructibleis_trivially_constructibleis_nothrow_constructible (C++11)(C++11)(C++11) is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible (C++11)(C++11)(C++11) is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible (C++11)(C++11)(C++11) is_move_constructibleis_trivially_move_constructibleis_nothrow_move_constructible (C++11)(C++11)(C++11) is_assignableis_trivially_assignableis_nothrow_assignable (C++11)(C++11)(C++11) is_copy_assignableis_trivially_copy_assignableis_nothrow_copy_assignable (C++11)(C++11)(C++11) is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable (C++11)(C++11)(C++11) is_destructibleis_trivially_destructibleis_nothrow_destructible (C++11)(C++11)(C++11) has_virtual_destructor (C++11) is_swappable_withis_swappableis_nothrow_swappable_withis_nothrow_swappable (C++17)(C++17)(C++17)(C++17) 關係與屬性查詢 is_same (C++11) is_convertibleis_nothrow_convertible (C++11)(C++20) is_layout_compatible (C++20) is_pointer_interconvertible_base_of (C++20) is_pointer_interconvertible_with_class (C++20)   is_corresponding_member (C++20) reference_constructs_from_temporary (C++23) reference_converts_from_temporary (C++23) is_base_of (C++11) is_virtual_base_of (C++26) alignment_of (C++11) rank (C++11) extent (C++11) is_invocableis_invocable_ris_nothrow_invocableis_nothrow_invocable_r (C++17)(C++17)(C++17)(C++17) 型別修改 remove_cvremove_constremove_volatile (C++11)(C++11)(C++11) add_cvadd_constadd_volatile (C++11)(C++11)(C++11) make_signed (C++11) make_unsigned (C++11) remove_reference (C++11) add_lvalue_referenceadd_rvalue_reference (C++11)(C++11) remove_pointer (C++11) add_pointer (C++11) remove_extent (C++11) remove_all_extents (C++11) 型別轉換 aligned_storage (C++11)(C++23 中已棄用) aligned_union (C++11)(C++23 中已棄用) decay (C++11) remove_cvref (C++20) result_ofinvoke_result (C++11)(直到 C++20*)(C++17) conditional (C++11) common_type (C++11) common_reference (C++20) underlying_type (C++11) type_identity (C++20) enable_if (C++11) void_t (C++17)
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integer_sequence (C++14)

 

定義於標頭檔案 <type_traits>
template< class T > struct remove_all_extents;		(C++11 起)

如果 T 是某種型別 X 的多維陣列，則提供成員 typedef type 等於 X；否則 type 是 T。

如果程式為 std::remove_all_extents 新增特化，則行為未定義。

成員型別

名稱	定義
型別	T 的元素型別

輔助型別

template< class T > using remove_all_extents_t = typename remove_all_extents<T>::type;		(C++14 起)

可能的實現

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; };

示例

執行此程式碼

#include <iostream>
#include <type_traits>
#include <typeinfo>
 
template<class A>
void info(const A&)
{
    typedef typename std::remove_all_extents<A>::type Type;
    std::cout << "underlying type: " << typeid(Type).name() << '\n';
}
 
int main()
{
    float a0;
    float a1[1][2][3];
    float a2[1][1][1][1][2];
    float* a3;
    int a4[3][2];
    double a5[2][3];
    struct X { int m; } x0[3][3];
 
    info(a0);
    info(a1);
    info(a2);
    info(a3);
    info(a4);
    info(a5);
    info(x0);
}

可能的輸出

underlying type: float
underlying type: float
underlying type: float
underlying type: float*
underlying type: int
underlying type: double
underlying type: main::X

參閱

is_array (C++11)	檢查型別是否為陣列型別 (類模板)
rank (C++11)	獲取陣列型別的維數 (類模板)
extent (C++11)	獲取陣列型別在指定維度上的大小 (類模板)
remove_extent (C++11)	從給定陣列型別中移除一個維度 (類模板)