i correct myself. a better example is [1, 2, 3, 1, 2, 3, 1, 2, 3]

sean, i think your explanation of 11.2d is a bit off. You do have a string of 3 substrings, but the question asks for lists and sublists. So would a more appropriate example be [123, 123, 123]?

Do I need to implement 11.2, 11.4, and 11.5 all in prolog?

Edited by author 03-02-2004 05:03 PM
Alaska - Thomas is correct only for part (a). For part (c), please use my interpretation: a list is the concatenation of zero or more runs R_i of elements, where each run R(e,n) consists of n identical elements e, n >= 0. Your job is to define a relation such that a list
    R(e_1,n_1) ... R(e_k, n_k)
is related to another list
    R(e_1,m_1) ... R(e_k, m_k)
where
    m_j = 1 if n_j > 1, and m_j = 0 otherwise.
In the example, "2" and "4" were not included in the output, because they were contained in runs of only a single element.

(11.2d) "abcabcabc" is a string consisting of three copies of the same substring, "abc".

i don't understand 11.2 part d. What does it mean by " a list is a concatenation of three copies of the same sublist". What does it mean by three copies of the same sublist? Thanks

Sean, I still don't understand your explanation. Could you tell me the difference between part a and part c. Is Thomas intepretation on part a and c correct?. Thanks

Edited by author 03-02-2004 12:58 PM
Lee - "relation" is the Prolog-word for "function" (more or less -- they're not the same thing). E.g. "parent(sean,peter)." defines the "parent" relation for "sean" and "peter".

TC -- I found this confusing as well. I interpret part C as "keep one copy of elements with adjacent duplicates, and no copies of anything else", e.g.

[1,1,2,3,3,4,5,5] ==> [1,3,5]

Unless someone else mentions an obviously better interpretation, let's stick with this one.

David -- you'll have to give me a bit more detail.

Edited by author 03-02-2004 04:39 AM
For problem 11.4, what is the difference between part a and part c? It seems to me that the question is poorly worded.

Here's how I've interpreted it:
Part a pairs [1,1,1,2,2,1,3] and [1,2,1,3].
Part c pairs [1,1,1,2,2,1,3] and [1,2,3].

In words:
In part a if a cluster of atoms is encountered, keep a single copy of that atom in the position of the cluster.
In part c if a cluster of atoms is encountered, keep a single copy of that atom in the position it is first encountered. Delete all other instances of that atom, even if they are not in a cluster.

This just doesn't seem correct, however.

for 11.4 what does that mean "define relation correponing to the operation". Can anyone give me an example? thnaks a lot.

For those of you who were in discussion today, here's a correct and functional implementation of bubble-sort in Prolog:

bsort([],[]).
bsort([A|B],[C|E]) :- bsort(B,D), bubble([A|D],[C|E]).

bubble([],[]).
bubble([A],[A]).
bubble([A,B|C], [A|D]) :- A < B, bubble([B|C], D).
bubble([A,B|C], [B|D]) :- A >= B, bubble([A|C], D).

How to run prolog... See

http://www.cs.ucsd.edu/classes/wi00/cse130/prolog.html

In particular: "Type sbprolog at the prompt to start the interpreter. If your prolog code is in a file named prologCode, type consult(prologCode) to load your program. It is better to avoid . character in file names.(That is, avoid file extensions for Prolog programs.) Type control-D to exit the interpreter."