1
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5
6 using System.IO;
7 using System.Concepts;
8
9 namespace System
10 {
11 public class Pair<T, U> where T is Semiregular and U is Semiregular
12 {
13 public nothrow Pair() : first(), second() {}
14 public Pair(const T& first_, const U& second_) : first(first_), second(second_) {}
15 public T first;
16 public U second;
17 }
18
19 public inline nothrow bool operator<<T, U>(const Pair<T, U>& left, const Pair<T, U>& right) where T is TotallyOrdered and U is TotallyOrdered
20 {
21 if (left.first < right.first) return true;
22 else if (left.first > right.first) return false;
23 else return left.second < right.second;
24 }
25
26 public inline nothrow bool operator==<T, U>(const Pair<T, U>& left, const Pair<T, U>& right) where T is Regular and U is Regular
27 {
28 return left.first == right.first && left.second == right.second;
29 }
30
31 public Pair<T, U> MakePair<T, U>(const T& first, const U& second) where T is Semiregular and U is Semiregular
32 {
33 return Pair<T, U>(first, second);
34 }
35
36 public class SelectFirst<T, U> : UnaryFun<Pair<T, U>, T> where T is Semiregular and U is Semiregular
37 {
38 public inline nothrow const T& operator()(const Pair<T, U>& p) const
39 {
40 return p.first;
41 }
42 }
43
44 public class SelectSecond<T, U> : UnaryFun<Pair<T, U>, U> where T is Semiregular and U is Semiregular
45 {
46 public inline nothrow const U& operator()(const Pair<T, U>& p) const
47 {
48 return p.second;
49 }
50 }
51
52 [system_default="true"]
53 public TextWriter& operator<<<T, U>(TextWriter& writer, const Pair<T, U>& pair)
54 {
55 return writer << "(" << pair.first << ", " << pair.second << ")";
56 }
57 }