Ciao-users April 2003

ciao-users@cliplab.org

9 participants
10 discussions

Re: [mail@krauskopf-rainer.de: functions in Ciao Prolog]
by Richard A. O'Keefe 30 Apr '03

30 Apr '03

Rainer Krauskopf <mail(a)krauskopf-rainer.de> wrote: 1. I can define in Prolog "between(+,?,+)" : between(A,A,B) :- A =< B . between(A,X,B) :- A < B , A1 is A + 1 , between(A1,X,B) . Please DON'T do that. For the last 20 years, the argument order of between/3 has been between(+LowerBound, +UpperBound, ?Element). Sample implementation: between(L, U, X) :- ( integer(L), integer(U) -> ( integer(X) -> L =< X, X = L =< U, between_aux(L, U, X) ; /* report type failure in X */ ) ; var(L), integer(U), integer(X), X > U -> fail ; integer(L), var(U), integer(X), X < L -> fail ; /* diagnose and report type failure or instantiation fault */ /* in L or U */ ). between_aux(L, L, L) :- !. between_aux(L, _, L). between_aux(L, U, X) :- M is 1 + L, between_aux(M, U, X). Part of the point of this is that the closure between(L,U) makes sense as a unary predicate, while *between(L,X) doesn't. However, it also follows the inputs-before-outputs principle, and is nicely consistent with numlist(L, U, [L,L+1,...,U]). ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Re: Bizarre Arithmetic with CIAO Prolog
by Richard A. O'Keefe 30 Apr '03

30 Apr '03

I wrote: > (2) Why are the extra digits at the end DIFFERENT from what one gets from > C? > (A2.1) Idunno, why ARE they different? Manuel Carro <mcarro(a)fi.upm.es> replied: Because printf is not used to generate and print the result. I'm afraid this misses the point of my question. The number is 1926/100.0. When I compare the output of printf("%.18e", 1926/100.0) with the output of (a copy of Dan Bernstein's implementation of) Taranto's algorithm, I get taranto(1.926000000000000156e+01) => 19.260000000000001563194018672220408916473388671875 That being so, a difference between CIAO output and printf() output may very well indicate an error in whatever method CIAO uses for binary->decimal conversion. It may not, of course. Perhaps in converting Dan Bernstein's code to ANSI C I introduced an error, so that printf() and taranto() are both wrong in exactly the same way. Perhaps. At least the question requires more serious examination than it has so far received. ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Re: Bizarre Arithmetic with CIAO Prolog
by Richard A. O'Keefe 29 Apr '03

29 Apr '03

There are two interesting questions about the 1926/100 example. (1) Why are there extra digits at the end? (A1.1) Because floating-point arithmetic is imprecise. (A1.2) Because the default behaviour is to show answers quite precisely. (Note: it is IMPORTANT to be able to write out a floating point number, read it back, and get the *SAME* number you started with. At one time Quintus Prolog got that wrong, VERY embarrassing. The Scheme standards actually require write/read round-tripping.) (2) Why are the extra digits at the end DIFFERENT from what one gets from C? (A2.1) Idunno, why ARE they different? ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Bizarre Arithmetic with CIAO Prolog
by Graeme Parkin 29 Apr '03

29 Apr '03

Dear All The following might help you to understand what is going on. It comes from a colleague Dr Maurice Cox: -------------------------------- This interesting example can be "explained" using the IEEE model of floating point arithmetic. The exact result of dividing a by b is X = a/b. Based on the IEEE model of fp arithmetic, the calculated result is x = (a/b)(1 + e), where |e| <= u, the unit roundoff. u = 2^{-52} = 2.2e-16 for Intel, Motorola, ... The error E in x is x - X = (a/b)e. Thus, |E| <= |a/b|u. For the example, a = 1926, b = 100, giving |E| <= (19.26)(2.2e-16) = 4.2e-15. The observed error using CIAO is 2.9e-15 and using C is 1.6e-15, both of which are consistent with the bound. This concept of fp error analysis is widely applicable to explain results and analyse and compare algorithms. ------------------------------- Best Wishes Graeme I Parkin Centre Mathematics and Scientific Computing National Physical Laboratory Queens Road Teddington, Middlesex TW11 0LW Tel: +44 20 8943 7104 Fax: +44 20 8977 7091 ------------------------------------------------------------------- This e-mail and any attachments may contain confidential and/or privileged material; it is for the intended addressee(s) only. If you are not a named addressee, you must not use, retain or disclose such information. NPL Management Ltd cannot guarantee that the e-mail or any attachments are free from viruses. NPL Management Ltd. Registered in England and Wales. No: 2937881 Registered Office: Teddington, Middlesex, United Kingdom TW11 0LW. ------------------------------------------------------------------- ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Re: functions in Ciao Prolog
by Manuel Hermenegildo 29 Apr '03

29 Apr '03

Rainer, sorry for the delay in answering more extensively. > I'm interested in Ciao Prolog. You claim that Ciao Prolog does support > programming with functions. What does this mean? Please be so kind and > let me have some examples: > 1. I can define in Prolog "between(+,?,+)" : > between(A,A,B) :- A = between(A,X,B) :- A A1 is A + 1 , > between(A1,X,B) . > I'd prefer to write : > between(A,A,B) :- A = between(A,X,B) :- A between(A + 1, X, B) . Simply load into Ciao the following file (it works exactly as you have written it!): :- module(_,_,[functions]). between(A,A,B) :- A = 2. I can define in Prolog "flin(+,-)" : > flin(X,Y) :- Y is 3*X + 5 . > I'd prefer to write : > flin(X) := 3*X + 5 . Simply add to the previous file: flin(X) := 3*X + 5 . And then, query: ?- flin(4,Y). Y = 17 ? (in fact, you can even express the "flin(+,-)" formally in the Ciao assertion language and this will be used by several tools, including LPdoc). > 3. I can define in Prolog "fak(+,-)" : > fak(0,1). > fak(N,Y) :- N > 0 , > N1 is N - 1 , > fak(N1,Y1), > Y is N*Y1 . > I'd prefer to write : > fak(0) := 1 . > fak(N) := N*fak(N - 1) if N > 0 . Simply add: fak(0) := 1 . fak(N) := N* ~fak(N - 1) :- N > 0 . The ~ is an 'eval' --the opposite of a 'quote'-- and it means that fak should be called, i.e., that it is not a data structure. You can also write :- function fak/1. fak(0) := 1 . fak(N) := N* fak(N - 1) :- N > 0 . to avoid the need to use the ~. > 4. I can define in Prolog "fib(+,-)" : > fib(0,0). > fib(1,1). > fib(X,Y) :- X > 1 , > X2 is X - 2 , > X1 is X - 1 , > fib(X2,Y2) , > fib(X1,Y1) , > Y is Y2 + Y1 . > I'd prefer to write : > fib(0) := 0 . > fib(1) := 1 . > fib(X) := fib(X - 2) + fib(X - 1) if X > 1 . The only difference is that for consistency we use :- instead of 'if': :- function fib/1. fib(0) := 0 . fib(1) := 1 . fib(X) := fib(X - 2) + fib(X - 1) :- X > 1 . or fib(0) := 0 . fib(1) := 1 . fib(X) := ~fib(X - 2) + ~fib(X - 1) :- X > 1 . > 5. I can define in Prolog "divides(?,+)" : > divides(X,Y) :- between(1,X,Y) , > 0 is Y mod X . > I can ask the questions : > ?- X is 3*4 , fak(3,Y) , fak(Y,Z) , divides(X,Z) . > ?- fak(4,Y) , divides(X,Y) . > ?- fib(4,X) , Y is 2*4 , fib(Y,Z) , divides(X,Z) . > ?- fib(6,Y) , fib(Y,Z) , divides(X,Z) . > I'd prefer to formulate : > ?- divides( 3*4 , fak(fak(3)) ) . > ?- divides( X , fak(4) ) . > ?- divides( fib(4) , fib( 2*4 ) ) . > ?- divides( X , fib(fib( 6 )) ) . What you want here is to activate the functional syntax in the top level. This can be done in the a the natural manner: ?- use_package(functions). {Including /home/clip/lib/ciao/ciao-1.9/library/functions/functions.pl {Including /home/clip/lib/ciao/ciao-1.9/library/functions/ops.pl } } yes ?- divides( 3*4 , ~fak(~fak(3)) ) . yes ?- divides( X , ~fak(4) ) . X = 1 ? yes ?- divides( ~fib(4) , ~fib( 2*4 ) ) . yes ?- divides( X , ~fib(~fib( 6 )) ) . X = 1 ? yes ?- > Is there a context sensitive help for built in predicates? Yes! Simply do C-c TAB while in the development environment (i.e., after opening a .pl file with emacs). Hope this helps! The Ciao Development Team -- ----------------------------------------------------------------------------- herme(a)fi.upm.es | Manuel Hermenegildo +34-91-336-7435 (Work) | Facultad de Informatica, UPM +34-91-352-4819 or 336-7412 (FAX) | Universidad Politecnica de Madrid http://www.clip.dia.fi.upm.es/~herme | 28660-Boadilla del Monte, MADRID SPAIN ----------------------------------------------------------------------------- ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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[mail@krauskopf-rainer.de: functions in Ciao Prolog]
by Manuel Hermenegildo 29 Apr '03

29 Apr '03

[We thought this might be of interest to other Ciao users] ------- Start of forwarded message ------- X-Coding-System: nil Return-Path: <mail(a)krauskopf-rainer.de> Date: Wed, 02 Apr 2003 18:58:27 +0200 From: Rainer Krauskopf <mail(a)krauskopf-rainer.de> Subject: functions in Ciao Prolog To: herme(a)clip.dia.fi.upm.es MIME-version: 1.0 X-Priority: 3 (Normal) Dear Manuel, I'm interested in Ciao Prolog. You claim that Ciao Prolog does support programming with functions. What does this mean? Please be so kind and let me have some examples: 1. I can define in Prolog "between(+,?,+)" : between(A,A,B) :- A =< B . between(A,X,B) :- A < B , A1 is A + 1 , between(A1,X,B) . I'd prefer to write : between(A,A,B) :- A =< B . between(A,X,B) :- A 0 , N1 is N - 1 , fak(N1,Y1), Y is N*Y1 . I'd prefer to write : fak(0) := 1 . fak(N) := N*fak(N - 1) if N > 0 . 4. I can define in Prolog "fib(+,-)" : fib(0,0). fib(1,1). fib(X,Y) :- X > 1 , X2 is X - 2 , X1 is X - 1 , fib(X2,Y2) , fib(X1,Y1) , Y is Y2 + Y1 . I'd prefer to write : fib(0) := 0 . fib(1) := 1 . fib(X) := fib(X - 2) + fib(X - 1) if X > 1 . 5. I can define in Prolog "divides(?,+)" : divides(X,Y) :- between(1,X,Y) , 0 is Y mod X . I can ask the questions : ?- X is 3*4 , fak(3,Y) , fak(Y,Z) , divides(X,Z) . ?- fak(4,Y) , divides(X,Y) . ?- fib(4,X) , Y is 2*4 , fib(Y,Z) , divides(X,Z) . ?- fib(6,Y) , fib(Y,Z) , divides(X,Z) . I'd prefer to formulate : ?- divides( 3*4 , fak(fak(3)) ) . ?- divides( X , fak(4) ) . ?- divides( fib(4) , fib( 2*4 ) ) . ?- divides( X , fib(fib( 6 )) ) . You see I'd appreciate the availability of the functional notation. What notation is available within Ciao Prolog? Is there a context sensitive help for built in predicates? Thank you in advance! Best regards R. Krauskopf ------- End of forwarded message ------- -- ----------------------------------------------------------------------------- herme(a)fi.upm.es | Manuel Hermenegildo +34-91-336-7435 (Work) | Facultad de Informatica, UPM +34-91-352-4819 or 336-7412 (FAX) | Universidad Politecnica de Madrid http://www.clip.dia.fi.upm.es/~herme | 28660-Boadilla del Monte, MADRID SPAIN ----------------------------------------------------------------------------- ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Re: Bizarre Arithmetic with CIAO Prolog
by Wamberto Vasconcelos 25 Apr '03

25 Apr '03

Quoting Bart Demoen <Bart.Demoen(a)cs.kuleuven.ac.be>: > It is perhaps official CIAO mailing list policy to be overpolite and > cautious in its response, but I am not one of the CIAO officials, so I > can butt in like an elephant in a porcelano shop ... You still are subject to the usual conventions of civilised behaviour, though. I know of floating point arithmetic, but I wanted to hear a proper technical explanation, particularly concerning the inconsistency of the results and whether it would be fixed in later versions (I now know it will). Your input to the discussion was patronising and unnecessary. -- Wamberto Vasconcelos, PhD wvasconcelos(a)acm.org Department of Computing Science http://www.csd.abdn.ac.uk/~wvasconc University of Aberdeen, Aberdeen AB24 3UE, Scotland, UK Phone +44 (0)1224 272283 Fax +44 (0)1224 273422 ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Re: Bizarre Arithmetic with CIAO Prolog
by Wamberto Vasconcelos 23 Apr '03

23 Apr '03

Dear CIAO users (and Jose Morales, in special) Thanks for your replies so far about my problems with arithmetic in CIAO. I would just like to add at this point that if I try the same division with other values, the long sequence of zeros won't appear. Check this: ?- X is 1927/100. X = 19.27 ? However, if I try ?- X is 1926/100. X = 19.2600000000000029 ? I am running CIAO version 1.8 and the specs of my machine (as requested by Jose Morales) are: Operating System Microsoft Windows XP Professional Version: 5.1.2600 Memory (RAM) Capacity: 512 MB Processor Intel(R) Pentium(R) 4 CPU 2.26GHz Version: x86 Family 15 Model 2 Stepping 4 Speed: 2253 MHz -- Wamberto Vasconcelos, PhD wvasconcelos(a)acm.org Department of Computing Science http://www.csd.abdn.ac.uk/~wvasconc University of Aberdeen, Aberdeen AB24 3UE, Scotland, UK Phone +44 (0)1224 272283 Fax +44 (0)1224 273422 ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Bizarre Arithmetic with CIAO Prolog
by Wamberto Vasconcelos 23 Apr '03

23 Apr '03

Folks One of my students drew my attention to the following unexpected result from CIAO: ?- X is 1926/100. X = 19.2600000000000029 ? Why is the "29" appearing at the end? Is this only happening in our current version? -- Wamberto Vasconcelos, PhD wvasconcelos(a)acm.org Department of Computing Science http://www.csd.abdn.ac.uk/~wvasconc University of Aberdeen, Aberdeen AB24 3UE, Scotland, UK Phone +44 (0)1224 272283 Fax +44 (0)1224 273422 ============================================================================== Message: Address: Action: help majordomo(a)clip.dia.fi.upm.es Info. on useful commands subscribe ciao-users-request(a)clip.dia.fi.upm.es Subscribe to this list unsubscribe ciao-users-request(a)clip.dia.fi.upm.es Unsubscribe from this list <whatever> ciao-users(a)clip.dia.fi.upm.es Send message to list ----------------------------------------------------------------------------- Archived messages: http://www.clip.dia.fi.upm.es/Mail/ciao-users/ -----------------------------------------------------------------------------

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Bizarre Arithmetic with CIAO Prolog
by Wamberto Vasconcelos 23 Apr '03

23 Apr '03

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Ciao-users April 2003