Could anyone who has Tutorial Letter 101 for 2009 please email it to me at ryuenzo [at] gmail [dot] com.

Thanks.]]>

So how was the paper for you all?

I don't know if feedback from students on the paper would be considered by the lecturers but it might be worthwhile to give some. I think it could help the lecturers to get a feel for the work they have done and how it was perceived by others, especially their students.

I found it wasn't to bad, not as bad as the preparation itself. One thing that bothered me was the fact that both the recursive definition and the inductive principle were asked. Although neither of them are very complicated the math inside the inductive principle could get a little tedious, especially for non-math majors such as myself. A real time waster in an exam.

Let's face it, this module is not a walk in the park and some of the principles can only be grasped with allot of practice. Unfortunately the exam schedule doesn't really allow for that, but that's besides the point. I think the lecturers MUST give more worked out examples of all the work, especially building FA's, TG's and regular expressions. It's fine to get some of the problems solved as is found in the study guide, but, I want to use the FA's and regular expressions as example. There's not really an algorithm in the textbook for building them. I think building TG's is a little bit better, but that can also be quite tedious to do. If you don't get practice in building these machines/expressions you would never be able to do it. The few samples in the text book and the few solved problems in the study guide is not nearly enough to enable a student like myself to start to recognize the patterns. I still until today cannot by just looking at the given problem build an FA or a regular expression or TG for that matter. I have to sit and try different possible solutions until I get the correct one, if ever. Unfortunately time is not really a student's best friend in the exams, so needless to say Question 5 had me wasting almost 20 minutes of my precious 120 available minutes, and still I couldn't get a correct working solution. I hope the markers will give me some marks for the about 10 different solutions I drew in the exam book before deciding to select one that looked possible, but wasn't working entirely for me. I just skipped question 6 for at that moment because I could earn some marks for some of the remaining questions in the time I had left.

With the previous paragraph I am trying to make the point that I really think the lecturers should put in an effort to try to get the students even more worked out samples, or they should try to explain the building of these machines/expressions in the study guide or an additional tutorial letter in such a way that it could be done with an algorithm or something like that. For me these are the most difficult parts of the module.

Unfortunately I couldn't complete questions 6 and 9 since I ran out of time. Damn that question 5. As mentioned earlier, I just skipped question 6 since it would have wasted more of my precious time.

I thought I could score a few marks for question 10, since it looked easy enough. I unfortunately made a huge mistake there. I mistaken the shortest path from - to + as a method to determine if an expression is finite or infinite. I knew the correct method using the formula and also looking for a loop, but my brain had another idea. I cannot even remember if their was a loop in it or not. I think that was a trick question since there was no way that you could get to + from -. It was clear that it was a infinite machine since their was this circuit that could be traveled infinitely, that I think wat the trick in the question in this case.

Question 9 would have given me 10 more marks since I get the Pumping Lemma and that particular one wasn't to complicated, but time was up. Again, damn that question 5, or was it me that didn't recognize the potential for more marks on question 9 than question 10.

I want to thank the lecturers for their time and effort of setting up the exam paper and as I already said it wasn't that bad. I though think one less question would have been the way to go. Maybe chose between the induction principle and the recursive definition or something like that. I think there is enough time during the assignments to test the understanding of both these concepts and in the exam time give the students a break from one of them.

OK, that's enough from me on this module. Only one more to go.

Hope you all do well in this paper and all the others.

From your fellow student,

Gert.]]>

While preparing for the exam, i came across these problems with the model answers for Assignment 1: Question 7 and 12.

Question 7:

Pg16 of Cohen states that the closure of the empty language contains the null string. Model answer for Q16 (option1) of assignment 1 also states this; which contradicts the model answer for Q7.

Question 12:

The model answer lists the 3rd option as correct where S* != T*; however the question was where S* = T*

Hopefully we will have up to 0.25% added to our final year mark because of this.

I have emailed the lecturers and will post their feedback.]]>

Thanks

B]]>

I have the assignments for 2006 and 2007 but no answers to check them against, can anybody help me out?

Thanks]]>

Please supply the answer for Q6 of the exam.]]>

Will an FA that does accept 0 length also be correct?

Thanks

B]]>

Anyone received past year exam papers with regards to COS201V/103/2008 tutorial letter.]]>

VV]]>

http://www.cs.usfca.edu/~jbovet/vas.html]]>

Could these be two FA's which describes L1 and L2? :S

Thanks,

Gert.]]>

So are all the other languages non-regular?

and then regular languages a sub set of these?

Thanks

B]]>

I assume we need to build the FA's.

Do need to see the steps?

regards

B]]>

Could anyone tell me which part of Kleene's theorem we have to use for questions 3 and 4?

I was able to get an NFA with 3 states by trail and error using the techniques from Chapter 5, but I don't know if we have to use one of the parts of Kleene's theorem.

The same goes for question 4.

According to theorem 7 p.137 of Cohen there is a FA for every NFA that accepts the exact same language. That I get. In proof two of theorem 7 p.138 of Cohen there is something written on the fact that the algorithm for producing FA* form FA should be used, or so it looks.

Am I on the right track for these questions or am I barking up the wrong tree.

Thanks for your replies in advance,

Gert.]]>

Are the results showing on your assignment 1 on MyUnisa?

My assignment 2 results are showing, but assignment 1 is still only pending. Not sure if there is an error somewhere.

Also, are we getting any admission credits for assignment2?

Cheers!

Francois]]>

This machine doesn't represent L

It also accepts b's, without any a's?

The second paragraph below the FA's has a sentence "It ignores all b's", so FA

Regards

B]]>

Not sure how to determine when no "dead-end" state is needed!

I do not see where in the algorithm for NFA to FA that this is determined.

Thanks

B]]>

Example on top of page.

The label on the edge from +x

Appreciated if someone can confirm. Thanks

B]]>

If we already have an FA, why ask us to build a new FA?

Or must we use the given FA to get a regular expression, and then build a new FA using the regular expression?]]>

This question is a bit misleading. I know it is after the fact, but checking through the answers. One of the requirements is all words with a length of three. The language name gives a clue of the language, but what if the language name is, for example, BOB. The answer will be the same, but the generators will be the only words in the language.

regards

B]]>

Statement B

The expression (ba + bb*a)* is to generate all words that do not contain aa over the alphabet {a,b}*. IMHO, the expression does generate words that do not contain aa, but not all words.

No words starting with ab are generated. So statement B is false.

regards

B]]>

I found a nice tool to help me with FA. It's called JFLAP - a JAVA applet that helps to evaluate FA,Turing machines etc. It's very easy to use and I found it quite helpful in checking whether my FA worked.

Its available for free download from http://www.jflap.org.

Note that this is a JAVA applet, so you need the JAVA runtime (available free from Sun if I remeber correctly)

Hope this can help somebody!]]>

Please confirm.

B]]>

Please check.

How many errors should be logged not mentioned in the errata, for the prize? (:P)

Regards

B]]>

I dont understand what the textbook is telling me?

Does S+ include the null string sysmbol or not, because S* certainly does.

My understanding is that it does not and that the first option would be false ie

A (S+)* = (S*)* is false

Am i correct?

Looking at the question again i c it has the closure symbol attached to it, so that means (S+)* would include the null string after all making the option True?

Am i correct?

Thx]]>

Is there a Computer Aided Lesson for COS201V as there was for Cos101?

The CD for COS101 realy helped me.

If there is what is the quickest way I can get hold of it?

(don't want to wait until exam time ye'know!)

Eugene]]>

Because none of them define all strings without bb.

In other words, most of them define strings without bb, but not all strings without bb.

Regards]]>