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Q2 2006

Posted by 35994908 
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Q2 2006
May 03, 2011 03:38PM
This is an attempt at Question 2. Please add any comments, as before, I don't claim this to be correct

avatar Re: 2006 Q2
May 03, 2011 05:09PM
I think you're going to come to grief on your second stage.

Imagine you have a word that ... no ... no I was seeing a whole bunch of a's on top of your stack, but you have something like this: cacaca-DELTAbottom. So you pop a c ... acaca-| and now you read a c (crash on anything else) ...

... Yes, and then pop an a (nothing else will do) : ... caca-| And read the next b... and so on.

Right and then you're READing an a ... You're expecting an a on the end of your input tape? Shouldn't this be straight on to DELTA? You're expecting the end of input now.

I think your top part is dead right, but that final straight should have a crash on a, and you should be expecting "ENDofINPUT" here.

I missed the exam paper when I did my last download from myUnisa.

Off topic: Have you gotten your assignment 2 back yet? I haven't seen any sign of 3 of my second assignments this semester. I'll have to do without whatever instruction my many mistakes in those might've given, I suspect. This is becoming quite common since they forced the science faculty to semesterise.

Maybe it's time to see if the SRC has any teeth? Put pressure on the administration to abandon this semester idea, and instead go for "overlapping years" - where you can start some year courses in June, and others, in January?

Certainly not now. And maybe this is something for those who have more years to go than us, too?
Re: 2006 Q2
May 03, 2011 05:33PM
Thanks for all the feedback, it's good to just think as well. It really helps!

If you read the last page of tutorial letter 104, it gave some pointers for the 2006 exam that they looked for. It says it must end in READ and POP delta before before going to ACCEPT

I am still waiting for Assignment 1, although I haven't checked my post for about 2 weeks. I agree with starting Yearly subjects in June and overlapping till the following year. Although there are some subjects that doing over a semester is really good and saves me from spending a whole year on a subject that I can complete over a semester, so that part is nice. I am however finding this a tricky subject.
avatar Re: 2006 Q2
May 03, 2011 06:06PM
No, your READ and your POP are fine, but it's how you get there that's not.

I mean you're going to accept the word acbca with this machine aren't you?

So your final READ is surely the one in the loop? Only it branches to accept on reaching delta.
Re: Q2 2006
May 05, 2011 11:13PM

Here is my DPDA:

I drew a transition table for it and it worked out with a tape containing acbca I also worked out the transition table for your DPDA and it also seems fine.
avatar Re: Q2 2006
May 05, 2011 11:53PM
Your POPs are conditional branches, so they need the diamond symbol. Or I think so anyway. Isn't it only the PUSH [somethingFromGamma] that are square? Each type of PUSH has its very own box, but they just have one branch out of them.

Pettifoggery aside, remember your READ reads the Tape, not the stack. Again you're saying that if the last thing you read on the Tape is an a, that's OK.

The question is: Is it? I see acbca being accepted here.... >>> and so he does what everyone responding should do, and reads the question a little bit more carefully ... >>> Mumble mumble ...

Sorry folks. Didn't see that the machines have to accept words ending on an a. Having feedback like that is quite a bit worse than just a bit of a nuisance. I suppose the moral of the story is when you're right, stick to your guns.

No, well then there's nothing to complain of. Both these machines work perfectly.
Re: Q2 2006
May 06, 2011 08:31AM
Thanks for that, I would go with yours. I think using X's to count after every occurance of ac is better. Nice!
Re: Q2 2006
May 06, 2011 10:25AM

But it took way to long to get the version you. Because I changed it 3 times, because I realized I made a mistake with the bc transitions but I caught it when drew the transition table using a example. So I'm definitely drawing a table in the exam! smiling smiley
avatar Re: Q2 2006
May 06, 2011 01:04PM
Yes, I like the X's. Have a separate "Gamma" so you make it nice and clear that you're using the stack for counting.

Have checked on that "diamond thing". Pop is definitely a diamond. Rationale: the symbol means there could be various branches emerging from this instruction. Your Pop could even shove a weasel off the stack?
Re: Q2 2006
May 06, 2011 01:45PM
Yip Thanks Eddy Pop is a diamond!
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