comp.lang.prolog Google Group

comp.lang.prolog Frequently Asked Questions

2010-01-03T10:38:25Z

Frequently Asked Questions - comp.lang.prolog
Last-modified: 2009-11-16
Last-changes: Mention irc.freenode.net's #prolog channel. Terrence Brannon.
Markus Triska (Mar. 2 2007 - ... )
Remko Troncon (Jan. 6 2002 - Mar. 2 2007)
Dirk-Jan Faber (Feb. 1 1999 - Jan. 6 2002)
Jamie Andrews (Aug 26 1992 - Oct. 16 1997)

Re: I love Prolog

2010-01-03T01:53:23Z

A beginners comment:
I haven't read "Learn Prolog Now", but have started with Bratko, simply
because I acquired that book some years ago (must have gotten
sidetracked). Apart from the earlier (minor) complaint about "different"
predicate, the book seems well written, and interesting. I managed to
complete first three chapters without serious problems (with all

Re: dif/2, an illustration

2009-12-31T13:59:07Z

But, who's goal is it `to learn Prolog'? I think more common goals are `to
learn (the) logic programming (paradigm)' or `how do I write/extend/... my app
X in Prolog Y'. Here, we must recognise that (almost?) all actively developed
and used Prolog implementations provide at least some constraints.

Re: dif/2, an illustration

2009-12-31T11:48:45Z

The main thing I am arguing for is 'please do sell CLP as Prolog':
if someone's goal is to learn Prolog (asking Bratko details) respect
that.
Promoting CLP is fine, but can those people also please explain to beginners
explicitly things like
dif(A,1), dif(B,2), dif(C,3), dif(D,4), dif(E,5),
perm2([1,2,3,4,5],[A,B,C,D,E]) ,

Re: dif/2, an illustration

2009-12-31T10:50:09Z

<snip>
Nice story. Only, this is a bit too long story to explain to beginners :-( I
guess there are two lines of thought that are -as far as I'm concerned-
equally defendable. One is to teach Prolog as a simple depth-first solver and
explain the pitfalls this creates and how to work around them. The other is

Re: dif/2, an illustration

2009-12-30T21:05:11Z

[...]
A discussion in three parts - first about the example at hand (I am sure
Chip realises what I am about to write, but I am also sure that most
people don't).
1. For this particular example, since the amount of filtered out
permutations is a constant fraction of the total amount (e-1/e) one
should not expect too much from any early filtering in terms of

Re: dif/2, an illustration

2009-12-30T19:39:58Z

Constraints can be very much be viewed as already part of resolution
algorithms. I think Alain Colmerauer should have shown this already
since when I remember well his Prolog II had a meta predicate
"geler", which translates to "freeze".
Such a meta predicate is able to instruct the interpreter to divert

Re: I love Prolog

2009-12-30T17:45:06Z

Walk through the P-99: Night-nine Prolog Problems,
[link] , and you will
learn a lot. :)
The elements for survival program is to describe a sentence "Water is
more important than food, and heat is even more important than water."
Interesting!

dif/2, an illustration

2009-12-30T16:35:34Z

The predicate dif/2 was proposed in A. Colmerauer's Prolog II language
in 1981. His later work in constraint logic programming is well-
known, and prompted by Markus Triska's enthusiasm for using this as
introductory element of Prolog, I formulate the follow example both to
illustrate the benefits of dif/2 and to elevate discussion of whether

Re: I love Prolog

2009-12-28T20:13:53Z

There is an online version at [link]
It is "old" but very good as a starter. Make sure you have SWI with you:
it is a hands-on book. Skip the part on DCGs.
This book will keep your enthusiasm high, and it does not dig deep:
you should be able to cover it in a few evenings.
After a while, you might want to look at books by Bratko

I love Prolog

2009-12-28T15:15:02Z

I'm nowhere near being a prolog expert. I dont know what difference
lists are, etc. But I love stating facts and having Prolog do the
rest.
I just wrote a computer program to calculate the importance of food
versus water versus heat in survival in Prolog:
[link]

Re: I.Bratko chapter #1

2009-12-28T15:03:36Z

Hi, Markus:
The "advanced topic" I meant was coroutining, without
which I don't see how to properly introduce dif/2,
any more than one can introduce =/2 without explaining
unification.
Likely my lack of familiarity with corouting in Prolog
and its contribution to constraint handling extensions
biases me.

Re: XPCE how to resize a picture?

2009-12-27T16:34:46Z

Ah, that's easier. Put the picture outside the dialog, both in a
frame.
Now the picture always fills the lower part of the window. Thank you.
-Jon

Re: XPCE how to resize a picture?

2009-12-27T14:37:31Z

But you don't want to append pictures to dialog windows. Windows
are designed to be grouped in frames. So, typically you'll see
send(new(P, picture), below, @sd)
--- Jan

Re: I.Bratko chapter #1

2009-12-26T17:37:22Z

Thanks for the encouragement (or are you trying to scare me off?) :-)
Just as long as you understand that you are talking here to the guy that
doesn't even know how to write 2 + 2 in prolog ... yet.
And no, I did not realize that /n is the arity. That was helpful.
- Hrvoje