35 lines
869 B
C#
35 lines
869 B
C#
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using System;
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using System.Collections.Generic;
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public delegate R Fun<A1,R>(A1 x);
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class MyTest {
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public static void Main(String[] args) {
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foreach (Object d in Map<int,int,String,Object>
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(delegate (int x) { return x.ToString(); },
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FromTo(10,20)))
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Console.WriteLine(d);
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}
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// Map with argument/result co/contravariance:
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// Aa=argument, Rr=result, Af=f's argument, Rf=f's result
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public static IEnumerable<Rr> Map<Aa,Af,Rf,Rr>(Fun<Af,Rf> f,
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IEnumerable<Aa> xs)
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where Aa : Af
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where Rf : Rr
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{
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foreach (Aa x in xs)
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yield return f(x); // gmcs 1.1.9 bug: cannot convert Aa to Af
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}
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// FromTo : int * int -> int stream
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public static IEnumerable<int> FromTo(int from, int to) {
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for (int i=from; i<=to; i++)
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yield return i;
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}
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}
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