[Asji]

            // Program asks user to enter password
            // If password is not "home", "lady" or "mouse"
            // the user must re-enter the password
            //Chapter 4 Debug 1

            const string PASS1 = "home";
            const string PASS2 = "lady";
            const string PASS3 = "mouse";
            string password;

            Console.Write("Please enter your password ");
            password = Console.ReadLine();
            while(password != PASS1 || password != PASS2 || password != PASS3)
            {
            Console.WriteLine("Invalid password. Please enter again. ");
            password = Console.ReadLine();
            }
            Console.WriteLine("Valid password");

            Console.ReadKey();

so there is my code, yet another debugging exercise
my problem arrives here

while(password != PASS1 || password != PASS2 || password != PASS3)

I'm not sure what type of bool goes here??
when I replace the != with ==, anything BUT the 3 accepted values returns a "Valid password"

and I'm not totally sure how to fix this error, I got all confused when I went here
http://msdn.microsof...=VS.100%29.aspx
hope that returns the right link/page and not just the default msdn page

thanks in advance for any help
/cheers

This post has been edited by Asji: 14 February 2011 - 10:53 PM

[Curtis Rutland]

Ok, first of all, what does "I'm not sure what type of bool goes here??" mean? Bool is a type. There's only one "type" of bool...and that's "bool".

Work the truth tables.

while(password != PASS1 || password != PASS2 || password != PASS3)

As your code is, the boolean statement will always result in true, because you're using ORs. If any one of those individual statements results in true, the entire statement is true, and since the password can't match all three, at least two will always be true. When you enter "home", the first one matches, means it is false. But the second one doesn't match, which is true, which means that the entire statement becomes true.

while (password == PASS1 || password == PASS2 || password == PASS3)

If you change them to "==", you have the opposite problem. The WHILE loop only executes when the statement equates to true, which means the stuff on the inside only runs when it's true. It will only be true when one or more of those statements results in true, which will only happen when you provide the right password.

Basically, you need to negate that entire statement. You need it to result in FALSE when it would be TRUE. To do so, use the Negation operator.

This post has been edited by insertAlias: 14 February 2011 - 11:06 PM

[maffelu]

I think you want to do this:

while(password != PASS1 && password != PASS2 && password != PASS3)

Since it can't be ANY of those you want to read

while(passwords is not PASS1 AND password is not PASS2 AND password is not PASS3)

[Asji]

Sorry about the initial confusion there

while(password != PASS1 || password != PASS2 || password != PASS3)

so what these != along with the OR ||, when the password is a correct value, it returns a false statement, but while the other 2 remain true
the OR || make the whole statement true?

[Curtis Rutland]

http://en.wikipedia....i/Boolean_logic

You need a good read on what bools actually are. When you use OR, if either side is true, the entire statement is true. When you use AND, both must be true. When there are no parenthesis, the equation is resolved from left to right. So, if I have:

A || B || C

First I evaluate A || B. Let's assume that evaluates to FALSE. Now the statement is :

FALSE || C

See how that works?

@maffelu, the idea here isn't to give out answers to homework. That doesn't impart any learning, just an answer. Please avoid just handing out solutions.

This post has been edited by insertAlias: 14 February 2011 - 11:24 PM

[Asji]

Yes it makes a lot more sense now!
Thanks a ton again
Sorry if I do ask some really easy questions, my professor don't really break it down to English very well.
We've gone through about 10 Chapters total in 2 books, and its really overwhelming for me

[Jeff H]

With what you learned so far can figure out what to replace ??? with to make it work?

 while(???(password == PASS1 || password == PASS2 || password == PASS3))  

[Asji]

I believe,

while(???(password == PASS1 || password == PASS2 || password == PASS3))

would be replaced with

while(!(password == PASS1 || password == PASS2 || password == PASS3))

as the ! would negate the value in quite an odd way, and I think it would work

[Curtis Rutland]

Quote

! would negate the value in quite an odd way

Nothing odd at all. ! is the negation operator. It takes true and makes it false, and it takes false and makes it true.

Boolean logic is just math. Parenthesis still have the highest order of operations, so the statement inside will be evaluated first.

We know from working the logic that the statement inside returns the exact opposite of what we want. So, we negate it with !.

This post has been edited by insertAlias: 15 February 2011 - 09:45 AM

[Asji]

thanks for nice explanation of how to use ! and !=
@maffelu,
Thanks for the ANSWER to the problem, but that's not quite what I was after, yes it did fix my problem, but with no explanation as to why it was a problem in the first place, nor a way to trouble-shoot a future problem of the same error with far more complexity.

Another thanks for this site and all the wonderful people that "troll" the forums to help "infants" like me
someday I hope to return the favor.
Thanks a ton!
/cheers