1. program TupleTest;
2.  
3. {$APPTYPE CONSOLE}
4.  
5. uses
6.   System.SysUtils;
7.  
8. type
9.   IgnoreElm = record end;
10.  
11.   Tuple<T1, T2> = record
12.   {$REGION 'Implementation details'}
13.   private
14.     type
15.       P1 = ^T1;
16.       P2 = ^T2;
17.       Tier = record
18.         Ref1: P1;
19.         Ref2: P2;
20.  
21.         class operator LessThanOrEqual(const Dest: Tier; const Src: Tuple<T1, T2>): boolean; overload;
22.       end;
23.   private
24.     class operator Implicit(const Value: Tuple<T1, T2>): Tuple<T1, IgnoreElm>;
25.     class operator Implicit(const Value: Tuple<T1, T2>): Tuple<IgnoreElm, T2>;
26.   {$ENDREGION}
27.   public
28.     Elm1: T1;
29.     Elm2: T2;
30.   end;
31.  
32.   Tuple = record
33.   public
34.     class function From<T1, T2>(const Value1: T1; Value2: T2): Tuple<T1, T2>; static;
35.     class function Tie<T1, T2>(var Elm1: T1; var Elm2: T2): Tuple<T1, T2>.Tier; overload; static;
36.     class function Tie<T1>(var Elm1: T1; const Ignored2: IgnoreElm): Tuple<T1, IgnoreElm>.Tier; overload; static;
37.     class function Tie<T2>(const Ignored1: IgnoreElm; var Elm2: T2): Tuple<IgnoreElm, T2>.Tier; overload; static;
38.   end;
39.  
40. const
41.   Ignore: IgnoreElm = ();
42.  
43. procedure Test;
44. var
45.   tup: Tuple<integer, string>;
46.   i: integer;
47.   s: string;
48. begin
49.   i := 123;
50.   s := 'bar';
51.  
52.   tup := Tuple.From<integer, string>(42, 'foo');
53.  
54.   Tuple.Tie(Ignore, s) <= tup;
55.  
56.   WriteLn(i, ', ', s);  // 123, foo
57. end;
58.  
59. { Tuple }
60.  
61. class function Tuple.From<T1, T2>(const Value1: T1; Value2: T2): Tuple<T1, T2>;
62. begin
63.   result.Elm1 := Value1;
64.   result.Elm2 := Value2;
65. end;
66.  
67. class function Tuple.Tie<T1, T2>(var Elm1: T1; var Elm2: T2): Tuple<T1, T2>.Tier;
68. begin
69.   result.Ref1 := @Elm1;
70.   result.Ref2 := @Elm2;
71. end;
72.  
73. class function Tuple.Tie<T1>(var Elm1: T1;
74.   const Ignored2: IgnoreElm): Tuple<T1, IgnoreElm>.Tier;
75. begin
76.   result.Ref1 := @Elm1;
77.   result.Ref2 := nil;
78. end;
79.  
80. class function Tuple.Tie<T2>(const Ignored1: IgnoreElm;
81.   var Elm2: T2): Tuple<IgnoreElm, T2>.Tier;
82. begin
83.   result.Ref1 := nil;
84.   result.Ref2 := @Elm2;
85. end;
86.  
87. { Tuple<T1, T2>.Tier }
88.  
89. class operator Tuple<T1, T2>.Tier.LessThanOrEqual(const Dest: Tier;
90.   const Src: Tuple<T1, T2>): boolean;
91. begin
92.   if (TypeInfo(T1) <> TypeInfo(IgnoreElm)) then
93.     Dest.Ref1^ := Src.Elm1;
94.   if (TypeInfo(T2) <> TypeInfo(IgnoreElm)) then
95.     Dest.Ref2^ := Src.Elm2;
96.   result := True;
97. end;
98.  
99. { Tuple<T1, T2> }
100.  
101. class operator Tuple<T1, T2>.Implicit(
102.   const Value: Tuple<T1, T2>): Tuple<T1, IgnoreElm>;
103. begin
104.   result.Elm1 := Value.Elm1;
105. end;
106.  
107. class operator Tuple<T1, T2>.Implicit(
108.   const Value: Tuple<T1, T2>): Tuple<IgnoreElm, T2>;
109. begin
110.   result.Elm2 := Value.Elm2;
111. end;
112.  
113. begin
114.   Test;
115.   ReadLn;
116. end.
117.