class template specialization
<utility>
std::tuple_element<pair>
| unspecialized | template <size_t I, class Tpl> class tuple_element; |
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| access first | template <class T1, class T2> struct tuple_element <0, pair<T1,T2>>; |
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| access second | template <class T1, class T2> struct tuple_element <1, pair<T1,T2>>; |
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Tuple element type for pair
Accesses the static type of the members of a pair object as if it was a tuple.
These class specializations simply provide a member called type, which aliases either T1 or T2, as if defined as:
1
2
3
4
5
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7
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template <size_t I, class Tpl> class tuple_element;
template <class T1, class T2> struct tuple_element <0, pair<T1,T2>>
{ typedef T1 type; };
template <class T1, class T2> struct tuple_element <1, pair<T1,T2>>
{ typedef T2 type; };
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See tuple_element for more information.
Template parameters
- I
- Order number of the element within the pair (zero-based).
This is 0 to access the type of member first and 1 to access the type of member second.
If instantiated with any other values, the program is ill-formed.
size_t is an unsigned integral type.
- Tpl
- Tuple-like type. For these specializations:
pair<T1,T2>.
- T1, T2
- Type of the elements in the pair.
Aliased as member type.
Member types
| member type | definition |
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| type | T1 if I is 0, or T2 id I is 1.
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