using System; using System.Collections.Generic;

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