In the beginning of a Prolog program I see: :-dynamic(path/1). It seems to be a clause that doesn't have a head. What does it mean?

I wrote the following simple code, and I expect that when I write 'male.', this code ask me once "is it male?" and if i input 'No' it write on screen "she is female". male :- ( print('is it male ...

What I have now checks that X(Y) is not an accepted fact in my small DB. Since X(Y) returns false it will attempt to assert it. (I realize this presents problems when X is a rule and not a fact) i...

Is there a Prolog implementation or library that caches predicates? Or would you implement a, say, FIFO cache using assertz/1 and retract/1, like this: :- dynamic cache/1. ccall(G) :- cache(G). c...

I would like to represent a mutable graph in Prolog in an efficient manner. I will searching for subsets in the graph and replacing them with other subsets. I've managed to get something working u...

If I want to make a rule dynamic so i can use assert after the database file has been loaded, how do i do it? I'm using XSB Prolog at the moment, the file is something like this: :- dynamic likes/...

I have this code in Prolog: dynamic(player_at/1). player_at(house). goto(X) :- retract(player_at(house)), assert(player_at(X)). But I still get this error: uncaught exception: error(permission_...