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  1. using System;
  2. using System.Collections.Generic;
  3.  
  4. public class Test
  5. {
  6.     public static void Main()
  7.         {
  8.         var l = new List<Union3<string, DateTime, int>>  {
  9.                 new Union3<string, DateTime, int>(DateTime.Now),
  10.                 new Union3<string, DateTime, int>(42),
  11.                 new Union3<string, DateTime, int>("test"),
  12.                 new Union3<string, DateTime, int>("one more test")
  13.         };
  14.  
  15.             foreach (Union3<string, DateTime, int> union in l)
  16.             {
  17.                 string value = union.Match(
  18.                     str => str,
  19.                     dt => dt.ToString("yyyy-MM-dd"),
  20.                     i => i.ToString());
  21.  
  22.                 Console.WriteLine("Matched union with value '{0}'", value);
  23.             }
  24.  
  25.         }       
  26. }
  27.  
  28. public sealed class Union3<A, B, C>
  29. {
  30.         readonly A Item1;
  31.         readonly B Item2;
  32.         readonly C Item3;
  33.         int tag;
  34.  
  35.         public Union3(A item) { Item1 = item; tag = 0; }
  36.         public Union3(B item) { Item2 = item; tag = 1; }
  37.         public Union3(C item) { Item3 = item; tag = 2; }
  38.  
  39.         public T Match<T>(Func<A, T> f, Func<B, T> g, Func<C, T> h)
  40.         {
  41.             switch (tag)
  42.             {
  43.                 case 0: return f(Item1);
  44.                 case 1: return g(Item2);
  45.                 case 2: return h(Item3);
  46.                 default: throw new Exception("Unrecognized tag value: " + tag);
  47.             }
  48.         }
  49.  }
Success #stdin #stdout 0.05s 33936KB
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stdin
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Standard input is empty
stdout
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Matched union with value '2013-08-19'
Matched union with value '42'
Matched union with value 'test'
Matched union with value 'one more test'
https://ideone.com/WZqhIb
language:
C# (gmcs 5.20.1)
created:
10 years ago
visibility:
public

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