CODEWITHSUNDEEP
c#
N. Bar
N. Bar

Reputation: 101

How to fix while loop stopping + unhandled exception error

While loops runs through the if statement once and stops.

I am new to c#, so excuse me if I am overlooking something seemingly obvious. I am currently writing a program that visualizes the Collatz conjecture through console entries. The program begins by prompting the user to enter a natural number. The program is supposed to run that number through the formulae of the conjecture until it eventually reaches a value of 1. However, when I type in the number in console, the program runs it through one formula and crashes. It seems that is has a problem with the Double.Parse line. I already tried using the convert method and tried defining "num" as a decimal instead of a double. 

    {
        Console.WriteLine("Enter a natural number:");

        Double num = Convert.ToDouble(Console.ReadLine());

        while (num != 1)
        {
            {
                if (num % 2 == 0)
                {
                    Console.WriteLine(num / 2);
                    num = Double.Parse(Console.ReadLine());
                }
                else
                {
                    Console.WriteLine(num * 3 + 1);
                    num = Double.Parse(Console.ReadLine());
                }
            }


            Console.ReadLine();
        }
    }
}
}

Upvotes: 0

Views: 130

Answers (1)

manic_coder
manic_coder

Reputation: 176

To be honest, I'm not positive what you're trying to achieve from the description (i.e., I have not idea what a Collatz conjecture visualization formula is), but I think I figured out what your issue is.

I think you're a little confused about Console.ReadLine(). This method pauses and waits for user input. As a result, during your first loop through the while statement, your program will pause and wait for user input. I think what you're trying to do is take the result of the formula in either the "if" or "else" section and capture that as the new value of "num."

Here is my best guess at what you're trying to achieve:

static void Main(string[] args)
    {
        Console.WriteLine("Enter a natural number:");

        Double num = Convert.ToDouble(Console.ReadLine());

        while (num != 1)
        {
            if (num % 2 == 0)
            {
                num /= 2;
                Console.WriteLine(num);
            }
            else
            {
                num = num * 3 + 1;
                Console.WriteLine(num);
            }
        }

        Console.WriteLine(num);

        Console.ReadLine();
    }

Also, it looks like you might have an extra set of brackets within your while statement. It doesn't seem like that would compile as-is, so perhaps it is just the way in which you copied it into your question.

Upvotes: 3

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