/* This program illustrates the use of "delegates", which allows for
   higher-order functions (that we saw in Scheme and Perl) in the context 
   of the oop type system.
*/

using System;

public delegate int intfun (int x);  // a delegate declaration

// A delegate is used like a class in that it can be instantiated with
// and function with type int->int.  Java has a similar mechanism where
// one can inline a class definition.

public class delegates
{
  public static int sqr(int x) { return x*x; }  // used to instantiate intfun
  public static int dec(int x) { return x-1; }  // used to instantiate intfun

  // apply a delgate function to every element of an array:  
  public static void map(intfun f, int[] A)
  { 
    for (int i=0;i<A.Length;i++) A[i] = f(A[i]);
  }
  
  public static void Main()
  {
     int[] A = {1,2,3,4,5,6,7,8,9,10};
     map(new intfun(sqr), A);  // square each number
     map(new intfun(dec), A);  // decrement each number
     foreach (int x in A) Console.Write(x+" ");
     Console.WriteLine();
  } // main
}

/* Output:
 
    0 3 8 15 24 30 3 8 15 24 35 48 63 80 99
*/