The difference between CLIPS and Prolog/Datalog is that CLIPS is a “production rule system” that operates by forward chaining: given a set of facts and rules, it will try to make every possible derivation of new facts and store those in memory. A query is then answered by checking whether it matches something in the … Read more
I’m assuming you are using swi interactively and trying to enter the fact gives you an error like so: 1 ?- like(x, y). ERROR: toplevel: Undefined procedure: like/2 (DWIM could not correct goal) Since the fact does not exist in the database. If this is the case, try asserting the fact first: 2 ?- assert(like(x,y)). … Read more
Prototyping. Prolog is dynamic and has been for 50 years. The compiler is liberal, the syntax minimalist, and “doing stuff” is easy, fun and efficient. SWI-Prolog has a built-in tracer (debugger!), and even a graphical tracer. You can change the code on the fly, using make/0, you can dynamically load modules, add a few lines … Read more
In SWI-Prolog: aggregate_all(count, is_man(X), Count).
The question has already been answered for Lisp, so I’ll just comment on Prolog. Prolog was designed for two things: natural language processing and logical reasoning. In the GOFAI paradigm of the early 1970s, when Prolog was invented, this meant: constructing symbolic grammars for natural language that would be used to construct logical representations of … Read more
Correct, this is a warning to enforce best practices, which is to put all related clauses together in the source file. Other than that, the proximity of clauses to each other in the source file does not matter, as long as their relative order does not change.
No, logic programming as embodied by those things and neo4j are quite different. On one level, you’re right that they conceptually both amount to graph storage and graph query. But for logic programming, it’s only conceptually graph query, there’s no guarantee that it’s actually stored that way (where with neo4j, it is). Second, with logic … Read more
In old-fashioned Prolog code, the following pattern arises rather frequently: predicate([], …). predicate([L|Ls], …) :- condition(L), then(Ls, …). predicate([L|Ls], …) :- \+ condition(L), else(Ls, …). I am using lists here as an example where this occurs (see for example include/3, exclude/3 etc.), although the pattern of course also occurs elsewhere. The tragic is the following: … Read more
It’s the ‘not provable’ operator. It succeeds if its argument is not provable (and fails if its argument is provable).
For each square, define X and Y variables that denote the upper left corner. These variable will have domains 1..10-L, where L is the length of the square. If you set the domain to 1..10, the squares may be placed partly outside your 10×10 rectangle. Then you can post constraints for each pair of rectangles … Read more