mcs/tests/gtest-iter-33.cs

   1 using System;
   2 using System.Collections.Generic;
   3
   4 public delegate R Fun<A1,R>(A1 x);
   5
   6 class MyTest {
   7   public static void Main(String[] args) {
   8     foreach (Object d in Map<int,int,String,Object>
   9                             (delegate (int x) { return x.ToString(); },
  10                              FromTo(10,20)))
  11       Console.WriteLine(d);
  12   }
  13
  14   // Map with argument/result co/contravariance:
  15   // Aa=argument, Rr=result, Af=f's argument, Rf=f's result
  16
  17   public static IEnumerable<Rr> Map<Aa,Af,Rf,Rr>(Fun<Af,Rf> f,
  18                                                  IEnumerable<Aa> xs)
  19     where Aa : Af
  20     where Rf : Rr
  21   {
  22     foreach (Aa x in xs)
  23       yield return f(x);    // gmcs 1.1.9 bug: cannot convert Aa to Af
  24   }
  25
  26   // FromTo : int * int -> int stream
  27
  28   public static IEnumerable<int> FromTo(int from, int to) {
  29     for (int i=from; i<=to; i++)
  30       yield return i;
  31   }
  32 }
  33
  34