How to resolve the algorithm Higher-order functions step by step in the C# programming language

Published on 12 May 2024 09:40 PM
#C_Sharp

How to resolve the algorithm Higher-order functions step by step in the C# programming language

Table of Contents

Problem Statement

Pass a function     as an argument     to another function.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Higher-order functions step by step in the C# programming language

C# Delegates:

Delegates are types in C# that represent methods with a specific signature. They allow you to pass methods as arguments to other methods or store them in variables.

Example 1:

In the first example, we define a delegate Func2 that represents a method taking two integer arguments and returning an integer. We then define three static methods (Add, Mul, and Div) that implement the addition, multiplication, and division of two integers, respectively.

The Call method takes a Func2 delegate, two integer arguments, and invokes the delegate with those arguments.

In Main, we create instances of the delegates and call Call to invoke the corresponding methods.

Example 2:

In the second example, we simplify the code by using anonymous delegate declarations. Instead of creating delegate instances explicitly using the new keyword, we use anonymous delegate expressions.

For example:

Console.WriteLine("f=Add, f({0}, {1}) = {2}", a, b, Call(delegate(int x, int y) { return x + y; }, a, b));

Example 3:

In the third example, we introduce lambda expressions, which are a concise way to define anonymous delegates using arrow syntax.

For example:

Console.WriteLine("f=Add, f({0}, {1}) = {2}", a, b, Call((int x, int y) => { return x + y; }, a, b));

In this example, the lambda expression (int x, int y) => { return x + y; } represents a delegate that takes two integer arguments and returns their sum.

Key Points:

  • Delegates represent methods as types.
  • You can create delegate instances using the new keyword or anonymous delegate expressions.
  • Lambda expressions are a concise way to define anonymous delegates.
  • You can invoke a delegate like a method by providing arguments that match its signature.
  • Delegates allow you to pass methods as arguments and store them in variables, providing flexibility and reusability in your code.

Source code in the csharp programming language

using System;

// A delegate declaration. Because delegates are types, they can exist directly in namespaces.
delegate int Func2(int a, int b);

class Program
{
    static int Add(int a, int b)
    {
        return a + b;
    }
    
    static int Mul(int a, int b)
    {
        return a * b;
    }
    
    static int Div(int a, int b)
    {
        return a / b;
    }
    
    static int Call(Func2 f, int a, int b)
    {
        // Invoking a delegate like a method is syntax sugar; this compiles down to f.Invoke(a, b);
        return f(a, b);
    }

    static void Main()
    {
        int a = 6;
        int b = 2;

        // Delegates must be created using the "constructor" syntax in C# 1.0; in C# 2.0 and above, only the name of the method is required (when a target type exists, such as in an assignment to a variable with a delegate type or usage in a function call with a parameter of a delegate type; initializers of implicitly typed variables must use the constructor syntax as a raw method has no delegate type). Overload resolution is performed using the parameter types of the target delegate type.
        Func2 add = new Func2(Add);
        Func2 mul = new Func2(Mul);
        Func2 div = new Func2(Div);
        
        Console.WriteLine("f=Add, f({0}, {1}) = {2}", a, b, Call(add, a, b));
        Console.WriteLine("f=Mul, f({0}, {1}) = {2}", a, b, Call(mul, a, b));
        Console.WriteLine("f=Div, f({0}, {1}) = {2}", a, b, Call(div, a, b));
    }
}


using System;

delegate int Func2(int a, int b);

class Program
{
    static int Call(Func2 f, int a, int b)
    {
        return f(a, b);
    }

    static void Main()
    {
        int a = 6;
        int b = 2;

        Console.WriteLine("f=Add, f({0}, {1}) = {2}", a, b, Call(delegate(int x, int y) { return x + y; }, a, b));
        Console.WriteLine("f=Mul, f({0}, {1}) = {2}", a, b, Call(delegate(int x, int y) { return x * y; }, a, b));
        Console.WriteLine("f=Div, f({0}, {1}) = {2}", a, b, Call(delegate(int x, int y) { return x / y; }, a, b));
    }
}


using System;

class Program
{
    static int Call(Func<int, int, int> f, int a, int b)
    {
        return f(a, b);
    }

    static void Main()
    {
        int a = 6;
        int b = 2;
        
                                                                 // No lengthy delegate keyword.
        Console.WriteLine("f=Add, f({0}, {1}) = {2}", a, b, Call((int x, int y) => { return x + y; }, a, b));

                                                                 // Parameter types can be inferred.
        Console.WriteLine("f=Mul, f({0}, {1}) = {2}", a, b, Call((x, y) => { return x * y; }, a, b));

                                                                 // Expression lambdas are even shorter (and are most idiomatic).
        Console.WriteLine("f=Div, f({0}, {1}) = {2}", a, b, Call((x, y) => x / y, a, b));
    }
}

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