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  #1 (permalink)  
Old October 31st, 2007, 02:46 PM
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Default implicit conversion

Ok, my current problem is that in my switch statement(below) I am having trouble with "implicitly trying to convert one type to another". At first I made a initiated a char that I used like

Code:
char testChar = myStack.Pop();

switch(testChar)
{
   /////
   code
   /////
}
 (From which I got an error about implicitly Converting char to str).
Additionally, I tried to just make the pop statement equal to a string value.

After that I just simply switched off of the value popped of the stack. (As seen in the code below). This time the error that was

: A value of an integral type expected

Also, this is part of a program designed to convert infix to prefix or postfix notation and vice versa... maybe that will provide a little insight as to my intentions.......
Help please?

P.S. I am sure some of you have probably seen this before, I just cleaned it up a bit and made a thread exclusive to this particular problem...



while(myStack.Count != 0)
            {
                switch(myStack.Pop())
                {
                    case "+":

                        if(operatorStack.Peek() == "*")
                        {
                            //lowerPrecedence = true;
                            strPostfix += operatorStack.Pop();
                        }
                        else if(operatorStack.Peek() == "/")
                        {
                            strPostfix += operatorStack.Pop();
                        }
                        else
                            operatorStack.Push(myStack.Pop());
                        break;

                    case "-":
                        if(operatorStack.Peek() == "*")
                        {
                            //lowerPrecedence = true;
                            strPostfix += operatorStack.Pop();
                        }
                        else if(operatorStack.Peek() == "/")
                        {
                            strPostfix += operatorStack.Pop();
                        }
                        else
                            operatorStack.Push(myStack.Pop());
                        break;

                    case "/":
                        //code
                        break;

                    case "*":
                        //code
                        break;

                    case "1":
                        strPostfix += myStack.Pop();
                        break;

                    case "2":
                        strPostfix += myStack.Pop();
                        break;

                    case "3":
                        strPostfix += myStack.Pop();
                        break;

                    case "4":
                        strPostfix += myStack.Pop();
                        break;

                    case "5":
                        strPostfix += myStack.Pop();
                        break;

                    case "6":
                        strPostfix += myStack.Pop();
                        break;

                    case "7":
                        strPostfix += myStack.Pop();
                        break;

                    case "8":
                        strPostfix += myStack.Pop();
                        break;

                    case "9":
                        strPostfix += myStack.Pop();
                        break;

                    case "0":
                        strPostfix += myStack.Pop();
                        break;

                }
            }
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Old November 1st, 2007, 04:13 AM
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Default

"1" is a string, whereas '1' is a character. You cannot implicitly convert a string to a char.

switch(testChar)
{
   case '1':
    // Do something
     break;
}

/- Sam Judson : Wrox Technical Editor -/
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Old November 1st, 2007, 09:37 PM
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Default

Actually, I fixed that before I posted the code. I copied this code out of my old thread. My bad. Anyways, I think I've figured out the differences in variable type, but the "if(operatorStack.Peek() = '*')" condition is throwing an error that states that
: The left-hand side of an assignment must be a variable, property or indexer. Any ideas on how to test this such that I can get away from these errors?

Also, what does it take to get an answer? I have done the work myself and made my problems as clear as possible, yet I'm not getting responses on this or other forums. I have been doing this project for nearly 2 weeks with only about 3 total responses. Would someone direct me to a beginners forum if that is the problem?? Or simply a forum where people will help me with this?
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Old November 2nd, 2007, 03:58 AM
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Should that not be "==" instead of "="?

If that was just a typo then let me know.

/- Sam Judson : Wrox Technical Editor -/
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Old November 3rd, 2007, 01:44 AM
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Default

No, I tried it both ways.

If I use a single '=' i get the ": The left-hand side of an assignment must be a variable, property or indexer." error.

If I use '==' I get an error stating ": Operator '==' cannot be applied to operands of type 'object' and 'char'"

Any suggestions on a smarter way to word that? Or perhaps a better conditional?
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Old November 3rd, 2007, 05:47 AM
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if('*' == (char)stack.Peek())

/- Sam Judson : Wrox Technical Editor -/
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Old November 4th, 2007, 03:43 AM
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Default

I had'nt thought of reversing it. Someone pointed out to me that I should probably convert my value popped off the stack to a string

i.e.
Code:
object nextItem = operatorStack.Peek();
if(nextItem.ToString() == "*" )
    {
        ///code
    }


It blew my mind that I never thought about that.

Seymour (AKA Simon)
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Old November 4th, 2007, 05:42 PM
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Default

Either way you are looking at boxing the char into an object and then back out again. If possible (i.e. if you're using .Net 2.0) I'd use Stack<char>.



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