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std::underlying_type

提供: cppreference.com
< cpp‎ | types

 
 
ユーティリティライブラリ
支援を入力します (basic types, RTTI, type traits)
動的なメモリ管理
エラー処理
プログラムユーティリティ
可変個引数関数
日付と時刻
関数オブジェクト
initializer_list(C++11)
bitset
hash(C++11)
関係演算子
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Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
ペアとタプル
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Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
フォワード、スワップ、および移動
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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)
 
支援を入力します
基本的なタイプ
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Basic types
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基本的なタイプ
固定幅の整数型 (C++11)
数値の限界
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Numeric limits
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numeric_limits
Cの数値は、インターフェイスを制限します
実行時型情報
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Runtime type information
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型の特徴
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Type traits
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プライマリタイプカテゴリ
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Primary type categories
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is_void(C++11)
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_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)
Typeプロパティ
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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)
is_abstract(C++11)
サポートされる操作
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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)
リレーションシップとプロパティクエリ
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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)
型の変更
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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)
型変換
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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)
形質定数を入力します
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Type trait constants
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integral_constant(C++11)
 
Defined in header <type_traits>
template< class T >
struct underlying_type;
(C + + 11以来)
列挙型の基になる型typeある型のメンバのtypedefTを定義しています.
Original:
Defines a member typedef type of type that is the underlying type for the enumeration T.
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[編集] メンバータイプ

名前
Original:
Name
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Definition
type
Tの基になる型
Original:
the underlying type for T
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[編集] ノート

各列挙型には、基底の型を持っています
Original:
Each enumeration type has an underlying type, which can be
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1。 (スコープとスコープを持たない列挙型の両方)を明示的に指定された
Original:
1. Specified explicitly (both scoped and unscoped enumerations)
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2。それはスコープの列挙または列挙型のすべての値(範囲外の列挙型)を表すことのできる実装定義の整数型のためintである場合には、省略されます
Original:
2. Omitted, in which case it is int for scoped enumerations or an implementation-defined integral type capable of representing all values of the enum (for unscoped enumerations)
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[編集]

#include <iostream>
#include <type_traits>
 
enum e1 {};
enum class e2: int {};
 
int main() {
    bool e1_type = std::is_same<
        unsigned
       ,typename std::underlying_type<e1>::type
    >::value; 
 
    bool e2_type = std::is_same<
        int
       ,typename std::underlying_type<e2>::type
    >::value;
 
    std::cout
    << "underlying type for 'e1' is " << (e1_type?"unsigned":"non-unsigned") << '\n'
    << "underlying type for 'e2' is " << (e2_type?"int":"non-int") << '\n';
}

Output:

underlying type for 'e1' is unsigned
underlying type for 'e2' is int