Why, do while or while loop?

Question

3.33/5 (3 votes)

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Since both are control flows, why have two(2) statements that have the same purpose? How do they differ?

do
{
//code here..
} while (bool == false);

while (bool == false);
{
//code here..
}

I mean sh*t, the only difference I see, is that one doesn't have a 'do' while the other one does. Sigh.

Posted 8-Apr-11 10:16am

Herboren

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Nish Nishant · Accepted Answer · 2011-04-08T10:29:00

Solution 3

It's quite simple. They are both loops that execute while a condition is true. One checks the condition before the loop, the other checks it after the loop. This leads to one being 0 or more times, and the other 1 or more times. That's all. So you pick one of them based on that requirement.

Posted 8-Apr-11 10:29am

Nish Nishant

Comments

Espen Harlinn 8-Apr-11 17:54pm

Nice and simple reply :)

Nish Nishant 8-Apr-11 18:10pm

Thanks Espen!

Sergey Alexandrovich Kryukov 8-Apr-11 19:52pm

Sure, a 5.
--SA

Nish Nishant 9-Apr-11 8:35am

Thank you!

Albin Abel 9-Apr-11 0:40am

Clear answer. My 5

Nish Nishant 9-Apr-11 8:34am

Thank you!

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-04-08T10:26:00

Solution 2

For different logics. Condition is not checked in the very beginning in first cases, but is checked in the second case. Your example will not compile (bool is the reserved word, must be a variable). Now, consider it is a variable, say Condition. Then (Condition == false) make no sense, use (!Condition). You're trying to make Boolean from a Boolean, makes no sense.

Now, you cycles are infinite. Why? In real life the condition should be re-calculated in each cycle. When you do that, you will see the difference. For example, with the fist construct you cannot make a loop running 0 times — first iteration always run, with the second one you can, as condition may be true or false, depending in its calculation.

Now, posting question like that makes little or no sense. Read the manual first, with sample. Asking such question is very ineffective and waste your time, as well as others'.

—SA

Posted 8-Apr-11 10:26am

Sergey Alexandrovich Kryukov

Comments

Herboren 8-Apr-11 16:40pm

That was just an example cause im at work I cant whip something up fast enough to prime my question, but I understood what Naerling posted. The question seemed perfect to everyone else, honestly 2 people answered what i was looking for. =) Maybe it was the lack of punctuation that threw you off.

Sander Rossel 8-Apr-11 16:41pm

I think you kind of missed the point of the question... He was simply asking for the difference between the two, the syntax is just an example.
Edit: Oops, Herboren beat me to it ;)

Sergey Alexandrovich Kryukov 8-Apr-11 19:57pm

Are you serious? missed the point? How about your logic? Perhaps you think a question like "what's the difference between {0} and {1}" is valid? Thank think again.
And I guess you voted accordingly?
(Just a note: I'm not going to vote; and frankly, this question does not deserve any answer at all; jut RTFM would be quite enough).
--SA

Sander Rossel 9-Apr-11 5:11am

Well, if you put it like that it might have been something he could have looked up himself. But I for one, did not even know there was a Do While. By Herboren posting this question others may also learn from it. Besides, he asked a clear question, using <pre> tags and in understandable English. That alone deserves a good answer (even just a link where it is explained). Maybe you have heard of "There are no dumb questions"? And note that "gimme codez plz" is not a question :)
So while your answer is a good and detailed one I do not like the attitude that comes with it.

Herboren 8-Apr-11 16:43pm

Lol moar fail, its okay Naerling, you answered my question and that all that matters.

Sergey Alexandrovich Kryukov 8-Apr-11 19:58pm

RTFM, that's all what matters. So many times I wanted to avoid answering such questions...
--SA

Herboren 8-Apr-11 20:47pm

If you didn't want to answer the question, then don't answer, no one asked you to take your precious time to come here to look for an argument. Now had I said, "Oh gracious and most knowledgeable, SAKryukov, come to thy rescue!", it would be different, but I see the fiction yet to be true and will surely not happen in the future, so don't get caught up on nonsensical abstraction.

Sergey Alexandrovich Kryukov 8-Apr-11 21:28pm

I already answered.

I would kindly asked you not to be so rude. All you accusations are all in you mind. You assume to much, based on your emotions. Also, I would rather reserve my right to decide what answer to provide in what case. In this case, I provide a pretty complete answer. You either made or mistake of not seeing it or lie. What is it really -- you choose.

Best wishes.
--SA

Espen Harlinn 8-Apr-11 17:49pm

Good effort as usual :)

Sergey Alexandrovich Kryukov 8-Apr-11 19:50pm

Thank you Espen. If you say so; not wonder somebody voted 1 and 2, and Naerling thinks I'm missing the point -- "asking the difference" -- kind of stupid.
--SA

Herboren 8-Apr-11 20:19pm

Perhaps you are missing the point because not everyone thinks on the same level as you. Perhaps if you took the time to understand and accept that people who may have or have not RTFM, is because what you perceive as general knowledge by or acquired knowledge, doesn't me the world will revolve or 'evolve'(change for you) for that matter because it somehow just seems that best way. There are people out there that are geniuses because they think by symbols and patterns, and as long as it works for them, then what is the use in knowledge itself. People struggle to get where their at right now, so you need to take that 5 second delay and understand what you say before you actually say it rather assume what seems to be the worst in people. You can have all the back up in the world, hell they can help you hang your dirty clothes out to dry it it floats your boat, but I will tell you one thing, and attempt to belittle or discriminate against ones knowledge and how they should see things will just get your ass chewed out.

Sergey Alexandrovich Kryukov 8-Apr-11 21:25pm

First, you did not even try to explain what I'm missing in my Answer.

It looks you just go personal and feel RTFM note to be offensive. I don't think so and apply the same to myself. All your blaming is purely emotional and is not based on any facts. I know this phenomena very well; some people tend to get offended on any mistake corrected by others. If you tool the labor of looking on how I admit my mistakes or weaknesses and how much real help I delivered to people (beginners or not) you would never write such things.

You fail to see I am keeping to the facts as I see them and act in favor of OP. What this person really need is not facts but a bit of shock: come on, get to work. Your speculations about seconds, discrimination, etc., are not based on any fact. You're talking attitudes. May be you we shouldn't.

Happy coding.
--SA

Albin Abel 9-Apr-11 0:39am

Hi Herboren. I understood you just asked for the difference. But from the answer of SAKryukov you got some more information on the proper syntax and its logic. Why don't you take this extra information in the positive way? By the way welcome to code project community.

Sergey Alexandrovich Kryukov 9-Apr-11 1:05am

Thank you Albin. I knew some of great people here would support me.
--SA

Sergey Alexandrovich Kryukov 8-Apr-11 21:45pm

Sorry, Herboren, I did not realize in my message above *you* are the OP.
Very nice of you! I give you the most detailed answer, and you accuse me as I refused to answer.
What didn't you understand then? Of the offer to read the manual made you furious?
May be that was you who down-voted this Answer by the way?
Please tell me, I hope you're not a coward. I really don't think you are...

And by the way, I would gladly come to help, despite somewhat hard discussion... :-)

Thank you.
--SA

Albin Abel 9-Apr-11 0:40am

my 5+ for the answer and the time spent here.

Sergey Alexandrovich Kryukov 9-Apr-11 1:07am

Thank you very much, Albin.
--SA

Herboren 9-Apr-11 12:29pm

You know of all the forums I have been to everyone has the same output, I am here to learn but telling me im wasting my time as well as others, I think I have every right to display such an emotional response. Maybe it did not occur to you that I have tried reading the manual and trying the samples and examples but still not understood how it works. Did you ever stop to think about that? Just because you understand it and I don't doesnt give you any right to make such statements. Try a little professionalism, it could have prevented this. It doesnt hurt to mentor someone but when your tenure with your reputation and bolster in such a way of the knowledge you have, you tend to put off a negative effect because there is no control in this forum. If this were a paying job i'm sure you would have been disciplined very quickly on your actions. There was nothing wrong with my question, whether it made no sense to you or little sense at all, it got answered period. Im satisfied with the answer I received but not satisfied with you so this discussion is over with, I am not going to entertain myself anymore, this post can be pruned off now, btw I enjoy being here at the forum and I thank you for the welcome s(^.-)-b

Albin Abel 9-Apr-11 12:42pm

Hi Herboren. We appreciate your interest in learning. I hope you got necessary information for your question?. Post your questions if any. Cheers

Sander Rossel · Accepted Answer · 2011-04-08T10:21:00

Solution 1

I just found this...
A while loop might never execute a statement if the expression is false but a do while will always execute the statement at least once.

Sounds logic, since your first example does something and checks an expression after that while your first example first checks if it needs to do something.

Here is the link I found: http://cplus.about.com/od/learningc/ss/clessonfive_4.htm[^]

Posted 8-Apr-11 10:21am

Sander Rossel

Comments

Herboren 8-Apr-11 16:27pm

Ok so to use an loose anology:

while()
I am the while at the beginning and I am the lock, you can not access my statement unless your expression is true!

do while()
I will let you process my statements once or possibly more than once, but if I find your expression to be true then you are no longer allowed to process what I have to offer!

I know it sound ghey but, please tell me I hit the nail on the head?

Espen Harlinn 8-Apr-11 17:48pm

>> if I find your expression to be true then
>> you are no longer allowed to process what
>> I have to offer!

You got it exactly wrong - the loop will execute until the expression evaluates to false, I think SAKryukov and Nishant made a teriffic effort to head you in the right direction.

Sander Rossel 8-Apr-11 17:56pm

Oh, only noticed that now :)
Should be true, not false.

Espen Harlinn 9-Apr-11 3:08am

OK :)

Sander Rossel 8-Apr-11 16:35pm

Yeah, that's it.

Herboren 8-Apr-11 16:37pm

Sweet, ty sir you have been great! s(^.-)-b