回答編集履歴
4
m
answer
CHANGED
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@@ -3,6 +3,7 @@
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3
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イメージとしてはこんなのを作ります。
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```cpp
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+
namespace inferior{
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template<bool b>
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using enable_if_t = typename std::enable_if<b, std::nullptr_t>::type;
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template<bool b>
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@@ -26,6 +27,7 @@
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using require_input_iterator = enable_if_t<
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inferior::is_input_iterator<InputIter>::value
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>;
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+
}
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29
31
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```
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30
32
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31
33
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実際のSTLの実装を見てみてもそうなっていますね。
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3
mi
answer
CHANGED
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@@ -7,13 +7,6 @@
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7
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using enable_if_t = typename std::enable_if<b, std::nullptr_t>::type;
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template<bool b>
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using bool_constant = std::integral_constant<bool, b>;
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10
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template<typename...> struct conjunction : std::true_type {};
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template<typename B1> struct conjunction<B1> : B1 {};
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12
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template<typename B1, typename... Bn>
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struct conjunction<B1, Bn...>
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: std::conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};
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15
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template<typename B>
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struct negation : bool_constant<!bool(B::value)> {};
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template<typename...>
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using void_t = void;
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template<typename T, typename = void>
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2
l
answer
CHANGED
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@@ -37,4 +37,5 @@
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37
37
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38
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実際のSTLの実装を見てみてもそうなっていますね。
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39
39
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40
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-
msvc: [https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508](https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508)
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40
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+
msvc: [https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508](https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508)
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41
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libstdc++: [https://github.com/gcc-mirror/gcc/blob/d61d2a5f3ce9238bad7cbd7733d90c6ec7ae5fbc/libstdc%2B%2B-v3/include/bits/stl_vector.h#L651-L654](https://github.com/gcc-mirror/gcc/blob/d61d2a5f3ce9238bad7cbd7733d90c6ec7ae5fbc/libstdc%2B%2B-v3/include/bits/stl_vector.h#L651-L654)
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1
e
answer
CHANGED
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@@ -1,3 +1,40 @@
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1
1
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SFINAEでイテレーターであることを確認していると思います。
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2
2
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3
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+
イメージとしてはこんなのを作ります。
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4
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+
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5
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```cpp
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6
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template<bool b>
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7
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using enable_if_t = typename std::enable_if<b, std::nullptr_t>::type;
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8
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template<bool b>
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9
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using bool_constant = std::integral_constant<bool, b>;
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10
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template<typename...> struct conjunction : std::true_type {};
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11
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template<typename B1> struct conjunction<B1> : B1 {};
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template<typename B1, typename... Bn>
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struct conjunction<B1, Bn...>
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: std::conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};
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15
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template<typename B>
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16
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struct negation : bool_constant<!bool(B::value)> {};
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17
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template<typename...>
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18
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using void_t = void;
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19
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template<typename T, typename = void>
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20
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struct is_iterator : std::false_type {};
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21
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template<typename T>
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struct is_iterator<T, void_t<typename std::iterator_traits<T>::iterator_category>>
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: std::true_type
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{};
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25
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template<typename Iterator, bool is_iterator = is_iterator<Iterator>::value>
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struct is_input_iterator : std::false_type {};
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27
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template<typename Iterator>
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struct is_input_iterator<Iterator, true> : std::is_base_of<
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std::input_iterator_tag,
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typename std::iterator_traits<Iterator>::iterator_category
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> {};
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32
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template<typename InputIter>
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33
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using require_input_iterator = enable_if_t<
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34
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inferior::is_input_iterator<InputIter>::value
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35
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>;
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36
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```
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37
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+
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38
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+
実際のSTLの実装を見てみてもそうなっていますね。
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39
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+
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3
40
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msvc: [https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508](https://github.com/microsoft/STL/blob/ac4fde764ae716512bdd67e0e9577bd53947bc3d/stl/inc/vector#L507-L508)
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