D120.de/forum

Hi all, in case you failed previous exams, you can now enroll in TUCaN for the re-examination in WS 2012/13 (TUCaN-ID 20-00-0072). The oral re-exam will take place on 5 Dezember 2012 , starting at 11:00, and will be held in room A212, the office of Prof. Mezini. We will notify you by mail after the ...

For those of you who have failed the written exam, there will be a re-examination in the next winter term. In all likelihood, this will be an oral exam (30-45 minutes) taking place in early December 2012. The bonus points you have earned in the SS 2012 will be transferred over to the oral exam in WS...

TUCaN came back online - while I was on vacation for a few days. Sorry for the delay. :-( Unfortunately, TUCaN doesn't seem to offer the functionality to delete Lehrmaterial , which makes me not want to use it for publishing the PDF of preliminary grades there. (I wonder who did the requirements ana...

While TUCaN doesn't support publishing preliminary results out of the box, I think I have come up with a way to make the full list of preliminary results available to you in TUCaN (once it is back online again): I'll attach it as Lehrmaterial to the lecture. That way, it is visible (over an encrypte...

I finished marking the exam rather quickly :-). The resulting preliminary grades and (bonus) points can be found on the pinboard next to S2|02-A207, my office. Please have a look. If there are any questions or you want to have a look at your exam and how it was marked, please drop by at my office. I...

A is correct: ... I don't see why this is = g(A(g)), but I know A is correct (used above...) :-/ Let me redo the derivation, as I think the last step went wrong: A(g) = ((lambda (x) (g (lambda (v) ((x x) v)))) (lambda (x) (g (lambda (v) ((x x) v))))) = (g (lambda (v) (((lambda (x) (g (lambda (v) ((...

For lazy evaluation and immediate substitution I however still only see a way to implement this using somethink like cyclic environments. If you don't believe that immediate substitution works, give https://cage.st.informatik.tu-darmstadt.de/2012/copl/public/lectures/2012-04-26/fwae-immediate-subst...

Name 3 different ways to implement recursion. global function declarations cyclically bound environments use recursion of underlying, interpreting language (meta-interpretation) [Y/fix-point combinator] There is also a fifth way: dynamic scoping . (If you don't believe me, try it out with the inter...

Regarding "free instances of identifiers": Is it correct that every program with any free identifiers is semantically incorrect? I guess in Scheme and Haskell that would be the case but in some languages (Python? Ruby? Perl?) you can define a special behaviour if the program tries to interpret an u...

Well, I understood what's meant, however only rather contrived examples come to my mind (except for the combine vs. combine2 task 5 from ex. 2012-05-11) I admit that it's not trivial to come up examples. One way to construct one would be a version of the function that requires length l to be known ...

For call-by-name, I agree with you. For call-by-need, the question is whether (+1 1) is an "argument" or not. If it is, (+ 1 1) would have to be calculated just once. From there one, we need to run f(2) twice as we only cache arguments, not function values for certain arguments. Finally, the outer ...

One question though: The following expression is erroneous (as the interpreter says) - how comes? let foo = unsafePerformIO . getLine Well, what are the types involved? getLIne :: IO String unsafePerformIO :: IO a -> a (.) :: (b -> c) -> (a -> b) -> (a -> c) So, the problem is simply that getLine i...

5.3 Discuss existence of "unsafePerformIO :: IO a -> a". As this was never mentioned in the lecture or exercise and so I have to look it up online (which is no option on Friday :wink:), I'm very uncertain about my following solution: the operation is not type-safe I/O operation enclosed should be f...

Yes, exactly. Also, Felix's note that (define f (lambda (x) ...)) == (define (f x) ...) is important, as you need to insert the call to Y between the define f and the (lambda (x) ...) body. As for the step function: I can see why this might be confusing, but the name simply stems from the fact that ...

Yes, we distinguish between caching and memoization . In the former case the (single-value) cache is attached to expression closures (which makes it lazy-evaluation only), whereas in the latter case the (multi-value) cache is attached to either function closures or fun-def s (if using first-order fu...