iso-prolog

问题 Assume I have the following DCG rule: factor(X) --> "(", expr(X), ")". Normally this would be translated to: factor(X, A, B) :- [40|C] = A, expr(X, C, D), [41|B] = D. Would a Prolog system be allowed to translate it as follows, i.e. to merge the unifications into the head and the goal? factor(X, [40|A], B) :- expr(X, A, [41|B]). If DCG expansion would not be steadfast, it wouldn't be allowed to put [41|B] in the third argument of the expr call. But I guess steadfastness is in place, so

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . Is there a description of Prolog language (syntax and semantics) available online? There are a lot of reference manuals for implementations. But neither of those is a language description. For example the SWI Prolog manual states This manual does not describe the full syntax and semantics of Prolog. And refers

问题 ISO-Prolog (ISO/IEC 13211-1:1995 including Cor.1:2007, Cor.2:2012) offers the following built-in predicates for testing the type of a term: 8.3 Type testing 1 var/1. 2 atom/1. 3 integer/1. 4 float/1. 5 atomic/1. 6 compound/1. 7 nonvar/1. 8 number/1. 9 callable/1. 10 ground/1. 11 acyclic_term/1. Within this group there are those whose purpose is solely to test for a certain instantiation, that is 8.3.1 var/1 , 8.3.7 nonvar/1 , 8.3.10 ground/1 , and those that assume that a term is sufficiently

问题 I encountered several times Key-Value pairs in the SWI-PL doc but couldn't get a good info about them. Is this something standard in prolog or is it just a swi pl only extension ? Mainly found here : http://www.swi-prolog.org/pldoc/doc_for?object=keysort/2 and here : http://www.swi-prolog.org/pldoc/doc_for?object=section%282,%27A.3%27,swi%28%27/doc/Manual/assoc.html%27%29%29 The form of the pairs is a-5 for example, or in a list [a-5, b-7]. And if it is standard, is there any added value to

问题 This question already has answers here : Is floating point math broken? (31 answers) Closed 5 years ago . I find the result very strange. Why not 0.3? Can somebody tell me why this result? Is it possible to fix this. ?- X is 5.3-5. X = 0.2999999999999998. ?- My second question is how would I transform from 'hour' notation '13.45' ---->'15.30' into numbers of hours ? For example the period above calculated 15.30-13.45 would be 1.85. But I need to operate on parts of the hour and not the

问题 I have a problem with defining procedures in Prolog. I have two source files and want to consult Prolog engine with both of them. This can be done by invoking Prolog as swipl -g “['1.pl','2.pl']. Both of the files are generated by another program written in another programming language and i can't predict the exact content of the files beforehand. The problem is that in one of the files there is always a rule predicate1(X):-predicate2(X). But,sometimes the rule predicate2(something):-body

问题 I am trying to find the minimum value of a list (as a learning experience, so without min ). My approach is the following: minimo([X], X). minimo([X,Y|Tail], N):- (X > Y, minimo([Y,Tail], Y)); (X <= Y, minimo([X,Tail], X)). This gives me the following error: Syntax error: Operator expected So my questions are: What is causing the syntax error? I will try it myself once that is fixed if it actually gives the correct value back, but would this actually be a correct approach? Thanks in advance.

问题 I'm trying to find a way to append a list to all lists within a list. Something like: appendAll([a,b],[[q,w],[z,x]],X). X = [[a,b,q,w],[a,b,z,x]]. I'm still new to prolog and nested lists are throwing me off quite a bit. I've been staring at this for a few hours now: appendAll([], _, []). appendAll(_, [], []). appendAll([H1|T1], [H2|T2], X) :- append(H1,H2,R), appendAll(T1,[H2|T2],X). % recurse down to [], and append back up Any help is much appreciated Thanks! 回答1: What is difficult in

问题 I was looking through the SICStus manual's syntax description and there is a definition of "float". However, there is no indication of what the implementation of "float" actually is. IEEE single or double precision? Maybe even a BigDecimal ? In SWI Prolog (or at least SWISH), the "float" seems to be IEEE double precision, as can be determined via: planck_float(P) :- planck_float_descent(1.0,P). planck_float_descent(X,P) :- Xhalf is X / 2.0, Xtest is 1.0 + Xhalf, Xtest =\= 1.0, !, write(Xhalf)

问题 I just stumbled over the definition of ;/2 in the SWI Prolog Manual which states: The `or' predicate is defined as: Goal1 ; _Goal2 :- Goal1. _Goal1 ; Goal2 :- Goal2. Wouldn't that mean that ;/2 behaves exactly as if we wrote our own helper predicate consisting of two rules? I had memorized that ;/2 was an impure construct (but it's possible I'm mixing this up with if-then-else) but this definition is pure (although meta-logical). The semantics of ;/2 are defined in the ISO standard in