October 2004 - PPL-devel - BUGSENG Mailman

ppl TODO
by Enea Zaffanella 20 Oct '04

20 Oct '04

CVSROOT: /cvs/ppl Module name: ppl Changes by: zaffanella(a)cs.unipr.it 2004-10-20 15:15:51 Modified files: . : TODO Log message: The bug concerning empty generator systems has been fixed. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/ppl/TODO.diff?cvsroot=ppl&r1=1.10…

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[Fwd: Re: Any Prolog language lawyer out there?]
by Roberto Bagnara 20 Oct '04

20 Oct '04

-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: 20 Oct 2004 08:17:19 GMT From: Jan Wielemaker <jan(a)ct.xs4all.nl> Reply-To: jan at nospam.swi.psy.uva.nl Organization: SWI, University of Amsterdam Newsgroups: comp.lang.prolog References: <41750912.8040102(a)cs.unipr.it> <1098196164.417498(a)seven.kulnet.kuleuven.ac.be> <slrncnaat8.jkn.jan(a)ct.xs4all.nl> <87acuijutl.fsf(a)gondolin.bb.bawue.de> Jens, Thanks for clarifying. I do not have the official ISO text. Either this isn't correct in 'Prolog the Standard', or I missed this fragment (I do not have the book at hand right now). In article <87acuijutl.fsf(a)gondolin.bb.bawue.de>, Jens Kilian wrote: > Jan Wielemaker <jan(a)ct.xs4all.nl> writes: >> >| ?- functor(- 4,X,Y). >> > X = -4, >> > Y = 0 ? >> >> I think this is a mistake. Reading "Prolog, the standard", I find >> (p. 230) that an integer is an integer token, which is defined as a >> sequence of digits (besides binary, octal, etc). If this is really >> true, than negative numbers cannot be represented and only get their >> property when passed to one of the arithmetic predicates. > > My copy of a draft version of the standard (ISO/IEC JTC1 SC22 WG17 N110) > says > > 6.3.1.2 Negative numbers > > term = atom, integer; > Abstract: -n - n > Priority: 0 > > term = atom, float number; > Abstract: -r - r > Priority: 0 > > The prefix operator - with a numeric constant as operand > denotes the corresponding negative constant. > > This explicitly codifies the interpretation of '- 4' seen above. I do not like it ... > The tokenizer *cannot* consume the '-' in front of a number, because it may > need to be interpreted as an operator. Not even the presence or absence of > whitespace helps: > > X is Y-4. X is Y - 4. > > These must both be interpreted as is(X, -(Y, 4)). This is of course a bit undesirable as the tokeniser returns atoms, ints and floats as Prolog objects. Using 2-complement 32 bit ints, it cannot represent the token 2147483648. With your example Y-4 I started to wonder how I did this long time ago. Turns out the parser tells the tokeniser that the next token must be an operator (infix or postfix). If the tokeniser sees the next argument must be an operator it returns the atom '-', else the negative integer. Except for allowing for white-space this may actually be right. At any location where a term of the priority of the prefix operator - is allowes, it is also allowed to use an integer (priority 0), so the only reason to interpret the - in "-4" as an operator is if we need an infix operator at that place. It cannot even be interpreted as postfix, as the parser will fail afterwards on the "4" Writing terms -(number) is also interesting. The only valid representation is using (). Tested SICStus, Ciao, hProlog, gprolog, YAP and SWI-Prolog. SICStus, Ciao and SWI get this right. I'm tempted to accept "- 4" as the negative number -4 and print a style warning. Not in a hurry though :-) Does the official standard document document say anything about handling + in front of numbers? > Yes, this sucks. As does most of Prolog's syntax ;-) If it was the only thing that sucked, it would be almost perfect :-) Cheers --- Jan -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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[Fwd: Re: Any Prolog language lawyer out there?]
by Roberto Bagnara 20 Oct '04

20 Oct '04

-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: Wed, 20 Oct 2004 10:12:00 +0200 From: Bart Demoen <bmd(a)cs.kuleuven.ac.be> Organization: KULeuvenNet Newsgroups: comp.lang.prolog References: <41750912.8040102(a)cs.unipr.it> <1098196164.417498(a)seven.kulnet.kuleuven.ac.be> <slrncnaat8.jkn.jan(a)ct.xs4all.nl> <87acuijutl.fsf(a)gondolin.bb.bawue.de> Jens Kilian wrote: > This explicitly codifies the interpretation of '- 4' seen above. http://www.sju.edu/~jhodgson/prolog_proj/framed_spec.html has an executable ISO Prolog. One can submit goals and it tells you the result. Here are some examples related to -4: (I have removed some noise from the output) Goal : integer(- 4) Specification result : Must fail Goal : integer(-4) Specification result : Must succeed So it seems that the space between the - and the 4 is important. I do not have the final copy of the standard, and although I do remember that there has been discussion about it, I do not remember the final outcome, so can anybody check that's indeed what the standard says ? Cheers Bart Demoen -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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ppl/tests Makefile.am
by Roberto Bagnara 20 Oct '04

20 Oct '04

CVSROOT: /cvs/ppl Module name: ppl Changes by: roberto(a)cs.unipr.it 2004-10-20 13:25:44 Modified files: tests : Makefile.am Log message: Added nnc_randphull1 and nnc_randphull2 to DERIVED_TESTS. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/ppl/tests/Makefile.am.diff?cvsroo…

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[Fwd: Re: Any Prolog language lawyer out there?]
by Roberto Bagnara 20 Oct '04

20 Oct '04

-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: 19 Oct 2004 22:51:02 +0200 From: Jens Kilian <jjk(a)acm.org> Organization: 1&1 Internet AG Newsgroups: comp.lang.prolog References: <41750912.8040102(a)cs.unipr.it> <1098196164.417498(a)seven.kulnet.kuleuven.ac.be> <slrncnaat8.jkn.jan(a)ct.xs4all.nl> Jan Wielemaker <jan(a)ct.xs4all.nl> writes: > >| ?- functor(- 4,X,Y). > > X = -4, > > Y = 0 ? > > I think this is a mistake. Reading "Prolog, the standard", I find > (p. 230) that an integer is an integer token, which is defined as a > sequence of digits (besides binary, octal, etc). If this is really > true, than negative numbers cannot be represented and only get their > property when passed to one of the arithmetic predicates. My copy of a draft version of the standard (ISO/IEC JTC1 SC22 WG17 N110) says 6.3.1.2 Negative numbers term = atom, integer; Abstract: -n - n Priority: 0 term = atom, float number; Abstract: -r - r Priority: 0 The prefix operator - with a numeric constant as operand denotes the corresponding negative constant. This explicitly codifies the interpretation of '- 4' seen above. > I think this is undesirable. For one thing, on engines using fixed > with 2-complements representation (allowed!) one must write the > smallest integer as (-2147483647-1) !? No. I can see nothing in the (draft) standard which restricts the range of an 'integer' token; as I interpret it, a Prolog implementation using 16-bit integers is free to accept '- 32768' as a valid term and to reject '32768' as causing an integer overflow. > Also, one always needs is/2 to represent a negative integer. No, the parser has to convert negative numbers. > So, the tokeniser should deal with > '-'{digit}+. The situation for + is a bit less clear as it is not > _needed_ to represent positive integer terms. The tokenizer *cannot* consume the '-' in front of a number, because it may need to be interpreted as an operator. Not even the presence or absence of whitespace helps: X is Y-4. X is Y - 4. These must both be interpreted as is(X, -(Y, 4)). Yes, this sucks. As does most of Prolog's syntax ;-) Jens. -- mailto:jjk@acm.org As the air to a bird, or the sea to a fish, http://www.bawue.de/~jjk/ so is contempt to the contemptible. [Blake] -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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ppl ./CREDITS ./configure.ac demos/Makefile.am ...
by Roberto Bagnara 19 Oct '04

19 Oct '04

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ppl/interfaces/Prolog pl_check.pl Ciao/ppl_ciao.pl
by Patricia Hill 19 Oct '04

19 Oct '04

CVSROOT: /cvs/ppl Module name: ppl Changes by: hill(a)cs.unipr.it 2004-10-19 22:05:00 Modified files: interfaces/Prolog: pl_check.pl interfaces/Prolog/Ciao: ppl_ciao.pl Log message: Correction to ciao interface so it now allows for prolog failure for ppl_Polyhedron_map_space_dimensions/2 and ppl_Polyhedron_fold_dimensions/3. Negative tests for ppl_Polyhedron_map_space_dimensions/2 that caused make check when using pl_check.pl to fail have now been restored. Now these tests pass with all the Prolog systems. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/ppl/interfaces/Prolog/pl_check.pl… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/ppl/interfaces/Prolog/Ciao/ppl_ci…

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ppl demos/ppl_lcdd/ppl_lcdd.cc doc/devref-brow ...
by Roberto Bagnara 19 Oct '04

19 Oct '04

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[Fwd: Re: Any Prolog language lawyer out there?]
by Roberto Bagnara 19 Oct '04

19 Oct '04

-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: 19 Oct 2004 14:59:26 GMT From: Jan Wielemaker <jan(a)ct.xs4all.nl> Reply-To: jan at nospam.swi.psy.uva.nl Organization: SWI, University of Amsterdam Newsgroups: comp.lang.prolog References: <41750912.8040102(a)cs.unipr.it> <1098196164.417498(a)seven.kulnet.kuleuven.ac.be> In article <1098196164.417498(a)seven.kulnet.kuleuven.ac.be>, Bart Demoen wrote: > Roberto, > > >> Am I correct if I say that all the 6 tested systems are /not/ violating >> the ISO Prolog standard because unary plus is not mentioned in its Table 7 >> (p. 19) and thus its presence and priority are implementation-defined? >> All the best, >> >> Roberto >> >> P.S. Standard or not standard, I find all this quite striking. >> > > > The + not figuring in ISO as fy, makes the situation murky. But - is in ISO as 200 fy. > And one finds differences like: > > In SICStus: > >| ?- prolog_flag(language,_,iso). > yes >| ?- current_op(200,fy,-). > yes >| ?- functor(- 4,X,Y). > X = -4, > Y = 0 ? I think this is a mistake. Reading "Prolog, the standard", I find (p. 230) that an integer is an integer token, which is defined as a sequence of digits (besides binary, octal, etc). If this is really true, than negative numbers cannot be represented and only get their property when passed to one of the arithmetic predicates. I think this is undesirable. For one thing, on engines using fixed with 2-complements representation (allowed!) one must write the smallest integer as (-2147483647-1) !? Also, one always needs is/2 to represent a negative integer. So, the tokeniser should deal with '-'{digit}+. The situation for + is a bit less clear as it is not _needed_ to represent positive integer terms. Indeed a bit depressing ... Cheers --- Jan -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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[Fwd: Re: Any Prolog language lawyer out there?]
by Roberto Bagnara 19 Oct '04

19 Oct '04

-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: Tue, 19 Oct 2004 16:29:24 +0200 From: Bart Demoen <bmd(a)cs.kuleuven.ac.be> Organization: KULeuvenNet Newsgroups: comp.lang.prolog References: <41750912.8040102(a)cs.unipr.it> Roberto, > Am I correct if I say that all the 6 tested systems are /not/ violating > the ISO Prolog standard because unary plus is not mentioned in its Table 7 > (p. 19) and thus its presence and priority are implementation-defined? > All the best, > > Roberto > > P.S. Standard or not standard, I find all this quite striking. > The + not figuring in ISO as fy, makes the situation murky. But - is in ISO as 200 fy. And one finds differences like: In SICStus: | ?- prolog_flag(language,_,iso). yes | ?- current_op(200,fy,-). yes | ?- functor(- 4,X,Y). X = -4, Y = 0 ? while GNU-Prolog says: | ?- current_op(200,fy,-). yes | ?- functor(- 4,X,Y). X = - Y = 1 The old DEC-10 reader (used in e.g. SICStus) contains the clauses: read(atom(-), L, [Token-_|S1], Precedence, Answer, Layout, S) :- number_token(Token, Number), !, Negative is -Number, read_rest(S1, 0, Negative, L, Precedence, Answer, Layout, S). read(atom(+), L, [Token-_|S1], Precedence, Answer, Layout, S) :- number_token(Token, Number), !, Negative is +Number, read_rest(S1, 0, Negative, L, Precedence, Answer, Layout, S). which seem to be responsible for the behaviour above. I think not ISO at all. Moreover, if one retracts + as an operator, one should get syntax errors for +4, but here is SICStus again: | ?- op(0,fy,+). yes | ?- write(+4). 4 yes while GNU says: | ?- op(0,fy,+). yes | ?- write(+4). uncaught exception: error(syntax_error('user_input:2 (char:8) , or ) expected'),read_term/3) Cheers Bart Demoen -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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