comp.lang.prolog Google Group

comp.lang.prolog Frequently Asked Questions

tri...@logic.at (Markus Triska) — Sun, 03 Jan 2010 10:38:25 UT

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

hrvoje.blaze...@ri.t-com.hr (Hrvoje Blazevic) — Sun, 03 Jan 2010 01:53:23 UT

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

j...@hppc323.few.vu.nl (Jan Wielemaker) — Thu, 31 Dec 2009 13:59:07 UT

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

b...@cs.kuleuven.be (bart demoen) — Thu, 31 Dec 2009 11:48:45 UT

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

j...@hppc323.few.vu.nl (Jan Wielemaker) — Thu, 31 Dec 2009 10:50:09 UT

<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

b...@cs.kuleuven.be (bart demoen) — Wed, 30 Dec 2009 21:05:11 UT

[...]
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

janbu...@fastmail.fm (Jan Burse) — Wed, 30 Dec 2009 19:39:58 UT

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

g9414002.pccu.edu...@gmail.com (YauHsienHuang) — Wed, 30 Dec 2009 17:45:06 UT

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

hardm...@gmail.com (Chip Eastham) — Wed, 30 Dec 2009 16:35:34 UT

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

b...@cs.kuleuven.be (bart demoen) — Mon, 28 Dec 2009 20:13:53 UT

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

metap...@gmail.com (Terrence Brannon) — Mon, 28 Dec 2009 15:15:02 UT

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

hardm...@gmail.com (Chip Eastham) — Mon, 28 Dec 2009 15:03:36 UT

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?

jmil...@mitre.org (Jon) — Sun, 27 Dec 2009 16:34:46 UT

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?

j...@hppc323.few.vu.nl (Jan Wielemaker) — Sun, 27 Dec 2009 14:37:31 UT

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

hrvoje.blaze...@ri.t-com.hr (Hrvoje Blazevic) — Sat, 26 Dec 2009 17:37:22 UT

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