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  1. using System;
  2. using System.Reflection;
  3.  
  4. public delegate bool TryParser<T>(string s, out  T result);
  5.  
  6. public static class Parser
  7. {
  8.     public static bool TryParse<T>(string s, out T result)
  9.     {
  10.         return Inner<T>.parser(s, out result);
  11.     }
  12.  
  13.     public static T? ParseOrNull<T>(string s)
  14.         where T : struct
  15.     {
  16.         T result;
  17.         if (TryParse<T>(s, out result)) return result;
  18.         else return null;
  19.     }
  20.  
  21.     static class Inner<T>
  22.     {
  23.         public static TryParser<T> parser;
  24.  
  25.         static Inner()
  26.         {
  27.             var m = typeof(T).GetMethod("TryParse", new[] { typeof(string), typeof(T).MakeByRefType() });
  28.  
  29.             if (m == null)
  30.                 throw new NotSupportedException();
  31.  
  32.             parser = (TryParser<T>)Delegate.CreateDelegate(typeof(TryParser<T>), m);
  33.         }
  34.     }
  35. }
  36.  
  37. class Program
  38. {
  39.     static void Main()
  40.     {
  41.         Console.WriteLine(Parser.ParseOrNull<int>("1234"));
  42.         Console.WriteLine(Parser.ParseOrNull<int>("12a34"));
  43.         Console.WriteLine(Parser.ParseOrNull<int>("12344aq"));
  44.         Console.WriteLine(Parser.ParseOrNull<int>("123safw4"));
  45.         Console.WriteLine(Parser.ParseOrNull<double>("1.234"));
  46.         Console.WriteLine(Parser.ParseOrNull<double>("12.34"));
  47.         Console.WriteLine(Parser.ParseOrNull<double>("12.a34"));
  48.  
  49.         Func<string, byte?> parser = Parser.ParseOrNull<byte>;
  50.  
  51.         Console.WriteLine(parser("255"));
  52.     }
  53. }
  54.  
Success #stdin #stdout 0.05s 38184KB
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stdin
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Standard input is empty
stdout
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1234



1.234
12.34

255
https://ideone.com/YYKRj
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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