From: Jan Burse <janburse@fastmail.fm>
To: help-gnu-emacs@gnu.org
Subject: Re: How to improve the readability of (any) LISP or any highlevel functional language to the level of FORTH ?
Date: Sun, 02 Jan 2011 02:10:45 +0100 [thread overview]
Message-ID: <ifojao$73v$1@news.albasani.net> (raw)
In-Reply-To: <9e7a7683-a92a-4e88-a6f1-9e6a6bd2f057@z9g2000yqz.googlegroups.com>
The Quiet Center schrieb:
> %http://sites.google.com/site/prologsite/prolog-problems/1
>
> % Problem 1.08 - compress consecutive duplicates into a single
> % list element
>
> compress([], []).
> compress([X,Y], [X,Y]) :- X \= Y.
> compress([X,Y], [X]) :- X = Y.
>
> % problems writing other clauses (thanks RLa)
>
> compress([X,Y|Z], [X|Z1]) :- X \= Y, compress([Y|Z], Z1).
> compress([X,Y|Z], Z1) :- X = Y, compress([Y|Z], Z1).
>
The above code does not work fully correct. Here is a
counter example (try yourself):
?- compress([a],X).
No
In a Prolog introductory course I would anyway use:
% compress(+List,-List)
compress([X,X|L],R) :- !, compress([X|L],R).
compress([X|L],[X|R]) :- compress(L,R).
compress([],[]).
No reason to use (\=)/2, which is anyway not declarative,
and no reason to avoid the cut !/0.
Bye
P.S.: On sites.google.com I find the following solution,
correct, but also avoids the cut !/0:
% 1.08 (**): Eliminate consecutive duplicates of list elements.
% compress(L1,L2) :- the list L2 is obtained from the list L1 by
% compressing repeated occurrences of elements into a single copy
% of the element.
% (list,list) (+,?)
compress([],[]).
compress([X],[X]).
compress([X,X|Xs],Zs) :- compress([X|Xs],Zs).
compress([X,Y|Ys],[X|Zs]) :- X \= Y, compress([Y|Ys],Zs).
next prev parent reply other threads:[~2011-01-02 1:10 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-01 7:04 How to improve the readability of (any) LISP or any highlevel functional language to the level of FORTH ? girosenth
2011-01-01 11:39 ` Elena
2011-01-01 14:15 ` Pascal J. Bourguignon
2011-01-01 16:08 ` Nathan
2011-01-01 18:05 ` Jan Burse
2011-01-01 23:56 ` The Quiet Center
2011-01-02 1:10 ` Jan Burse [this message]
2011-01-02 3:45 ` LanX
2011-01-02 4:04 ` LanX
2011-01-02 5:36 ` Nathan
2011-01-02 6:46 ` Paul Rubin
2011-01-02 15:01 ` LanX
2011-01-02 15:14 ` Jerome Baum
2011-01-02 21:21 ` Paul Rubin
2011-01-02 7:14 ` w_a_x_man
2011-01-02 6:59 ` w_a_x_man
2011-01-03 15:22 ` LanX
2011-01-02 14:07 ` Frank GOENNINGER
2011-01-07 9:41 ` w_a_x_man
2011-01-09 10:41 ` How to improve the readability of (any) LISP or any highlevelfunctional " WJ
2011-01-03 10:29 ` How to improve the readability of (any) LISP or any highlevel functional " Didier Verna
2011-01-03 13:05 ` Tim Harig
2011-01-04 4:49 ` rusi
2011-01-04 5:39 ` D Herring
2011-01-04 8:02 ` Tim Harig
2011-01-04 9:09 ` Nicolas Neuss
2011-01-04 10:00 ` Tim Bradshaw
2011-01-04 12:21 ` Tim Harig
2011-01-04 12:23 ` Tim Bradshaw
2011-01-04 13:33 ` Tim Harig
2011-01-04 12:41 ` Tamas K Papp
2011-01-04 23:32 ` Tim X
2011-01-05 1:35 ` [OT] LISP community advocacy [was Re: How to improve the readability of (any) LISP or any highlevel functional language to the level of FORTH ?] Tim Harig
2011-01-05 9:52 ` How to improve the readability of (any) LISP or any highlevel functional language to the level of FORTH ? Tim Bradshaw
2011-01-04 6:24 ` Pascal J. Bourguignon
2011-01-04 15:43 ` Raffael Cavallaro
2011-01-04 10:18 ` Didier Verna
2011-01-01 22:50 ` girosenth
2011-01-02 21:11 ` Thien-Thi Nguyen
2011-01-03 16:21 ` José A. Romero L.
2011-01-03 18:03 ` jacko
2011-01-02 23:45 ` Chip Eastham
2011-01-01 18:27 ` How to improve the readability of Steve Revilak
2011-01-01 19:22 ` How to improve the readability of (any) LISP or any highlevel functional language to the level of FORTH ? prad
2011-01-01 23:56 ` Pascal Costanza
2011-01-02 5:39 ` D Herring
2011-01-02 14:17 ` Frank GOENNINGER
2011-01-02 14:53 ` Jerome Baum
2011-01-02 14:58 ` LanX
2011-01-02 17:55 ` Bernd Paysan
2011-01-03 18:07 ` jacko
2011-01-02 12:59 ` Doug Hoffman
2011-01-02 19:14 ` w_a_x_man
2011-01-03 5:20 ` Elizabeth D Rather
2011-01-03 10:48 ` MarkWills
2011-01-03 15:13 ` LanX
2011-01-03 18:20 ` jacko
2011-01-03 18:22 ` jacko
2011-01-03 10:18 ` Didier Verna
2011-01-04 6:47 ` pineapple
2011-01-04 14:14 ` P.M.Lawrence
2011-01-05 14:58 ` Xah Lee
2011-01-05 16:21 ` Andrew Haley
2011-01-05 21:29 ` Pascal J. Bourguignon
2011-01-06 8:57 ` Jonathan Groll
2011-01-07 5:36 ` Xah Lee
2011-01-07 13:28 ` Andrew Haley
2011-01-07 16:19 ` Xah Lee
2011-01-05 17:59 ` Elena
2011-01-05 20:13 ` Xah Lee
2011-01-05 21:42 ` Pascal J. Bourguignon
2011-01-06 13:38 ` Doug Hoffman
2011-01-06 19:20 ` Pascal J. Bourguignon
2011-01-07 0:09 ` w_a_x_man
2011-01-07 12:04 ` Doug Hoffman
2011-01-06 22:59 ` Xah Lee
2011-01-07 11:47 ` Jan Burse
2011-01-21 10:03 ` rupertlssmith
2011-01-21 16:08 ` Jan Burse
2011-01-21 21:43 ` D. J. Penton
2011-01-18 22:55 ` m_l_g3
2011-01-19 13:45 ` Doug Hoffman
2011-01-21 16:15 ` Jan Burse
-- strict thread matches above, loose matches on Subject: below --
2011-01-02 16:50 Drew Adams
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