asked on

Basic Recursion

I choose to print numbers 1 to 5 in this code. When I step through it using F11 I get to the line

return stval;

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It goes to the end of the routine, but does not go back to the calling command

printNatural(1, ctr);

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Instead it goes back to this line of code

return printNatural(stval + 1, ctr);

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several time before it goes back to the static main method.
Why does it not go straight back to static main after

return stval;

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using System;

namespace ConsoleApp10
{

    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("\n\n Recursion : Print the first n natural number :\n");
            Console.Write("---------------------------------------------------\n");
            Console.Write(" How many numbers to print : ");
            int ctr = Convert.ToInt32(Console.ReadLine());
            // Call recursive method with two parameters.	
            printNatural(1, ctr);
            Console.Write("\n\n");

        }
        static int printNatural(int stval, int ctr)
        {
            if (ctr < 1)
            {
                return stval;
            }
            ctr--;
            Console.Write(" {0} ", stval);
            return printNatural(stval + 1, ctr);
        }
    }
}

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ASKER CERTIFIED SOLUTION

it_saige

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AlHal2

ASKER

What would be a better implementation?

it_saige

Well in this instance, you want to simply print out numbers in sequence so a *better* implementation would do just that; e.g. -

using System;

namespace EE_Q29139617
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("\n\n Looping : Print the first n natural number :\n");
            Console.Write("---------------------------------------------------\n");
            Console.Write(" How many numbers to print : ");
            int ctr = Convert.ToInt32(Console.ReadLine());
            // Call recursive method with two parameters.	
            printNatural(ctr);
            Console.Write("\n\n");
            Console.ReadLine();
        }

        static int printNatural(int ctr)
        {
            for (int i = 1; i < ctr + 1; i++)
            {
                Console.Write(" {0} ", i);
            }
            return 0;
        }
    }
}

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Understand that this is not a recursive implementation. It is a looping implementation.

-saige-

AlHal2

ASKER

Thanks.

AndyAinscow

If you want to learn about recursion then:

        static void Main(string[] args)
        {
            Console.Write("\n\n Recursion : Print the first n natural number :\n");
            Console.Write("---------------------------------------------------\n");
            Console.Write(" How many numbers to print : ");
            int ctr = Convert.ToInt32(Console.ReadLine());
            // Call recursive method with two parameters.	
            printNatural(ctr);
            Console.Write("\n\n");
            Console.Read();
        }
        static int printNatural(int ctr)
        {
            if (ctr < 1)
            {
                return ctr;
            }
            Console.Write(" {0} ", ctr);
            ctr--;
            return printNatural(ctr);
        }

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which gives

AlHal2

ASKER

Thanks Andy. The example I chose was https://www.w3resource.com/csharp-exercises/recursion/index.php