tests/ltest-15.cs

   1 using System;
   2 using System.Collections.Generic;
   3
   4 static class Enumerable
   5 {
   6
   7         public static int Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, int> selector)
   8         {
   9                 return Sum<TSource, int> (source, (a, b) => a + selector (b));
  10         }
  11
  12         static TR Sum<TA, TR> (this IEnumerable<TA> source, Func<TR, TA, TR> selector)
  13         {
  14                 if (source == null)
  15                         throw new ArgumentNullException ("source");
  16                 if (selector == null)
  17                         throw new ArgumentNullException ("selector");
  18
  19                 TR total = default (TR);
  20                 int counter = 0;
  21                 foreach (var element in source) {
  22                         total = selector (total, element);
  23                         ++counter;
  24                 }
  25
  26                 if (counter == 0)
  27                         throw new InvalidOperationException ();
  28
  29                 return total;
  30         }
  31
  32 }
  33
  34 class Repro
  35 {
  36
  37         static int Main ()
  38         {
  39                 var sum = new [] { "1", "2", "3", "4", "5", "6", "7" }.Sum ((s) => int.Parse (s));
  40                 if (sum != 28)
  41                         return 4;
  42
  43                 Console.WriteLine (sum);
  44                 return 0;
  45         }
  46 }