Learning Goal: I’m working on a c# question and need a sample draft to help me learn.
using System;
using System.Collections.Generic;
namespace cse465 {
class DelegatesExample {
public delegate R Function<R, T>(T value);
public delegate R BinaryFunction<R, T1, T2>(T1 arg1, T2 arg2);
public static List<R> Map<R, T>(List<T> theList, Function<R, T> f) {
// TODO: implement the map operation, which you
// should be familiar with already from scheme
// But use a loop — not recursion!
List<R> result = new List<R>();
//Console.WriteLine(theList[1]);
// for (int i=0;i<theList.length;i++){
// result[i]=theList[i];
// }
return result;
}
public static R FoldLeft<R, T>(List<T> values, BinaryFunction<R, T, R> f, R init) {
// TODO: Implement the Fold Left
// You should be familar with it from scheme
// In case you arent — it is this pseudocode:
//
// for each item in the list, in reverse order:
// init = f(item, init)
// return init
return init;
}
public static void printIfEven(int x) {
if ((x % 2) == 0) {
Console.WriteLine($”{x,-6} – Even”);
} else {
Console.WriteLine($”{x,-6} – Odd”);
}
}
public static void printIfPositive(int x) {
if (x > 0) {
Console.WriteLine($”{x,-6} – Positive”);
} else if (x < 0) {
Console.WriteLine($”{x,-6} – Negative”);
} else {
Console.WriteLine($”{x,-6} – Zero”);
}
}
delegate void NumberHandler(int x);
public static void Main() {
List<string> values = new List<string>(Console.ReadLine().Split(‘,’));
Console.WriteLine($”Read in: {string.Join(“,”, values)}”);
List<int> numbers = Map<int, string>(values, Int32.Parse);
Console.WriteLine($”To Int: {string.Join(“,”, numbers)}”);
// Cube each number using a lambda expression
numbers = Map<int, int>(numbers, (x) => x*x*x );
Console.WriteLine($”Cubed: {string.Join(“,”, numbers)}”);
NumberHandler handler = null;
// TODO — add printIfEvens to the delegate `handler`
// TODO — add printIfPositive to the delegate `handler`
// This demonstrates the way delegate can be used as callbacks in C#
foreach (int n in numbers) {
if (handler != null){
handler(n);
}
}
}
}
}
Expect:
Read in: 1,-2,3,-4,10,11,-7,18
To Int: 1,-2,3,-4,10,11,-7,18
Cubed: 1,-8,27,-64,1000,1331,-343,5832
1 – Odd
1 – Positive
-8 – Even
-8 – Negative
27 – Odd
27 – Positive
-64 – Even
-64 – Negative
1000 – Even
1000 – Positive
1331 – Odd
1331 – Positive
-343 – Odd
-343 – Negative
5832 – Even
5832 – Positive
