> What Does
> What Does Cannot Set Meta Predicates Mean
What Does Cannot Set Meta Predicates Mean
When the method is used in a parametric category, its call is translated to a call to the built-in Prolog predicate arg/3. The following kinds of message are recognized by default: banner banner messages (used e.g. maplist(2, ?, ?) So what does that head mean? Defining a Module Importing Predicates into a Module Defining a meta-predicate meta_predicate/1 Overruling Module Boundaries Interacting with modules from the top level Composing modules from other modules Operators and modules Dynamic
no ?- X = Y, X == Y. The documentation for meta_predicate in SWI-Prolog is not exactly what I'd call the best-written prose in history. asked 1 year ago viewed 342 times active 1 year ago Upcoming Events 2016 Community Moderator Election ends Nov 22 Linked 26 Prolog map procedure that applies predicate to list elements This workaround is sometimes necessary when calling module meta-predicates whose meta-predicate templates are ambiguous and cannot be processed by the Logtalk compiler (note, however, that it's often possible to specify an
For a full programming example, see e.g. Similar to Prolog built-in predicates, these built-in methods should not be redefined. The use of non-classified variables in a lambda expression should be regarded as a programming error. See the description of meta_predicate/1 for details. :- module(maplist, [maplist/3]). :- meta_predicate maplist(2, ?, ?). %% maplist(:Goal, +List1, ?List2) % % True if Goal can successfully be applied to all %
Filed under: documentation, meta-predicates, blog, prolog COPYRIGHT © NOTICE: All content in my user folder falls under the WTFPL Version 2 unless otherwise specified. First, my_private_predicate isn't exposed in the module, so even if we could somehow trick the maplist module to use_module(my_module) (which we can't) it still wouldn't work. insert([H|T], It, [H|NewT]) :- H @< It, insert(T, It, NewT). Just a nice further example about lists of lists. ?- Xss = [[A],[B,C]], maplist(maplist(=(E)), Xss).
Currently, the ISO/IEC WG17 group is working on a draft specification for a definite clause grammars Prolog standard. In Prolog The directive allows both width/1 and side/1 to be used as messages to the object square. In the black box view, we look into an entity from an usage point-of-view using built-in methods for inspecting object operators and predicates that are within scope from where we are Join them; it only takes a minute: Sign up Prolog binding arguments up vote 2 down vote favorite In sicstus prolog, there's a predicate: maplist(:Pred, +List) Pred is supposed to take
Note that the order of the free variables is of no consequence (on the other hand, a list is used for the lambda parameters as their order does matter). share Share on Twitter Share on Facebook Email Link Like + Quote Reply chenks, May 13, 2012 chenks macrumors 6502a Joined: Oct 23, 2007 Location: UK #2 iAppleseed said: ↑ I Note that in this case the meta-predicate directive specifies that the closure will be extended with exactly one extra argument. The goal is something we supply to the predicate.
We may want to call the predicate which is masked out by the Logtalk lookup algorithm (see the Inheritance section) or we may need to call both predicates. Another common use for this directive is to solve conflicts when two inherited predicates have the same functor and arity. Prolog Predicate The libraries may want to print messages on its own, e.g. The Component argument is new in the Logtalk implementation and is useful to filter messages belonging to a specific component (e.g.
These methods cannot be used as messages to objects. The following predicate properties are supported: scope(Scope) The predicate scope (useful for finding the predicate scope with a single call to predicate_property/2) public, protected, private The predicate scope (useful for testing At the bottom level, you have the Logtalk compiler and runtime. In the latter case, PDT needs to intercept the Logtalk compiler and runtime messages to present the relevant information using its GUI.
one_or_more Predicate has one or more proofs. Please try the request again. insert(List, Term, NewList) adds Term to List (ordered and without repetitions) to obtain NewList, also ordered without repetitions. Then the weirdness begins.
As each Logtalk entity is compiled independently from other entities, this directive must be included in every object that contains a definition for the described predicate (even if the predicate declaration It is then followed by a comma-separated list of metapredicate heads and terminated by a period. maplist_([H0|T0], [H|T], Goal) :- call(Goal, H0, H), maplist_(T0, T, Goal).
In the body of a grammar rule, we can call rules that are inherited from ancestor objects, imported from categories, or contained in other objects.
The minimum information will be the instantiation mode of each argument. multifileTrue if there may be multiple (or no) files providing clauses for the predicate. Calling Prolog non-standard meta-predicates Prolog built-in meta-predicates may only be called locally within objects or categories, i.e. Mode directive Often predicates can only called using specific argument patterns.
I asked her what music I should listen to, and she said "I like electro music, and Drum and Bass, but ******* dubstep!". all_true(_, ). A more robust interface can be achieved using nth_clause/3 and clause_property/2. Meta-call methods Logtalk supports the generalized call/1-N meta-predicate.
Execution context methods Logtalk defines four built-in private methods to access an object execution context. These workflows are implemented as parametric objects allowing combining them to implement more sophisticated expansion workflows. b(3). It may sound unbelievable (to me too), but it really is happening.
Therefore, a clause such as: predicate(Arg) :- self(Self), atom(Arg), ... . A predicate call is compiled as a call to a local predicate if the object (or category) contains a scope directive, a definition for the called predicate, or a dynamic declaration Note that static objects may declare and define dynamic predicates. in the calling context, not in the meta-predicate definition context) we need to use the meta_predicate/1 directive.
login Powered by SWI-Prolog 7.3.30 Skip to content. | Skip to navigation Site Map Accessibility Contact Search Site only in current section Advanced Search… Sections HomeLanguagesIRCNewsEventsUsers Personal tools Log in Ys = [2,4,6] yes In this example, a lambda expression, [X,Y]>>(Y is 2*X), is used as an argument to the map/3 list mapping predicate, defined in the library object meta, in Where's the fix? After compiling and loading the above objects, you can use queries such as: | ?- main::a(X).
Logtalk supports the definition of meta-predicates that are called with closures instead of goals as long as the definition uses the Logtalk built-in predicate call/N to call the closure with the Any conflicts are reported by Logtalk as compilation errors. Here is a short example including calls to these three object execution context methods: :- object(test). :- public(test/0). It provides a asking predicate and a hook predicate, both declared and defined in the logtalk built-in object.
insert([H|T], It, [H|T]):- H == It. Both control constructs can be combined in order to call a goal from a grammar rule body, while bypassing at the same time the Logtalk compiler. exportedTrue if the predicate is in the public list of the context module. The reflection API supports two different views on entities and their contents, which we may call the transparent box view and the black box view.
The head-pattern is a compound term with the same name and arity as the predicate where each argument of the term is a meta-predicate specifier. Module=m2, Term = test ?- m1:meta(m2:test, x). all_true(Closure, [Arg| Args]) :- call(Closure, Arg), all_true(Closure, Args).