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