Use of unassigned variable 'result'. How do I fix this?

Question

1.00/5 (2 votes)

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C#

static void Main(string[] args)
        {
            Console.WriteLine("Enter a number:  ");
            Double num1 = Convert.ToDouble(Console.ReadLine());

            Console.WriteLine("Enter a 2nd number:  ");
            Double num2 = Convert.ToDouble(Console.ReadLine());

            Console.WriteLine("Enter an operator like +,-,*,/ :  ");
            string op = Console.ReadLine();

            calculate(num1, num2, op);
            Console.ReadLine();
            Console.WriteLine("thank you");
            Console.ReadLine();
        }

        static double calculate(double num1, double num2, string op)
        {
            

            double result;

            if (op == "+") 
            {
                result =(num1 + num2);
            }
            else if (op == "-")
            {
                result= num1 - num2;
            }
            else if (op == "*")
            {
                result = num1 * num2;
            }
            else if (op == "/")
            {
                result = num1 / num2; 
            }
            else
            {
                Console.WriteLine("Invalid operation");
            }
            return result;

        }
    }              
}

What I have tried:

I am building a simple calculator using Method.The problem is in the last line " return result;". Any help will be appreciated guys.

Posted 22-Jun-22 22:13pm

Sharyar Javaid

Updated 23-Jun-22 8:43am

CPallini

v3

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Tony Hill · Answer 1 · 2022-06-22T22:22:00

Solution 1

You need to set the result variable to a known value (see below) because when the method exits it tries to return result which does not have a value.

double result = 0;

Posted 22-Jun-22 22:22pm

Tony Hill

Comments

Sharyar Javaid 23-Jun-22 4:25am

Thanks Tony, but I already tried that. If I set double result = 0; . Yes It runs then but it still does not show the calculations . Only lets the user input 2 numbers and then exits. it doesnt even show 0 as result of calculation.

Tony Hill 23-Jun-22 4:31am

You did not mention that in the original question.

CPallini · Answer 2 · 2022-06-22T22:29:00

Solution 2

Quote:
Thanks Tony, but I already tried that. If I set double result = 0; . Yes It runs then but it still does not show the calculations . Only lets the user input 2 numbers and then exits. it doesnt even show 0 as result of calculation.

Replace

Quote:
calculate(num1, num2, op);

with

C#

double result = calculate(num1, num2, op);
Console.WriteLine("Result is  :  {0}", result);

Posted 22-Jun-22 22:29pm

CPallini

Comments

Sharyar Javaid 23-Jun-22 5:00am

Its working now! Can you please explain what you did there? especially what this line Console.WriteLine("Result is : {0}", result); is doing which my code without it couldn't do?Also I already defined a variable double for result in the 2nd method, why did you define it again in the main method since this line takes input from the 2nd method. doesn't it? thanks so much!

CPallini 23-Jun-22 5:09am

Your method correctly computes and returns a value that your original code simply discarded.

double result = calculate(num1, num2, op);

gets such a value and stores it in result.

Console.WriteLine("Result is  :  {0}", result);

shows the result to the world.

matblue25 · Answer 3 · 2022-06-23T08:43:00

Solution 3

You need to check that num2 is not zero before dividing.
This has nothing to do with your original question but will generate a divide by zero error if the user enters 0 for the 2nd number and "/" for the operation (try it!). Your code should be:

else if (op == "/") && (num2 != 0.0)

instead of

else if (op == "/")

You should always check that the denominator is not zero before dividing unless your calculation somehow assures that it cannot possibly be zero under any circumstances.

Posted 23-Jun-22 8:43am

matblue25

Comments

Sharyar Javaid 24-Jun-22 2:15am

THANKS man. but its still working brother beforehand. It doesnt give error but says infinity when divide by 0. which is right i guess.

matblue25 24-Jun-22 11:57am

A mathematician would say no. Anything divided by zero is undefined. If you divide a number by progressively smaller and smaller numbers, the result approaches infinity but that doesn't mean that dividing by zero equals infinity.
Wikipedia - Divide by zero

EDIT:
Also look at this thread - I didn't realize it but this is a well-known behaviour in C# .NET
CodeProject Thread on Divide by Zero