Question

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/2

likes(mary,tom)

when i try to consult the file with XSB i get an error:

? consult('D:\file.P).
not permitted to assert to static predicatelikes/2
forward continuation...blahblah

Any ideas?

Answer 1

The dynamic predicate works as you are expecting, so there is something else wrong if it is not working for you.

If test.P looks like this:

:- dynamic likes/2.

likes(mary,tom).

It can be consulted, and then more likes/2 facts can be asserted:

XSB Version 3.2 (Kopi Lewak) of March 15, 2009
[i686-pc-linux-gnu; mode: optimal; engine: slg-wam; scheduling: local; word size: 32]

| ?- consult('test.P').
[Compiling ./test]
[test compiled, cpu time used: 0.0440 seconds]
[test loaded]

yes
| ?- assert(likes(mary, bob)).

yes
| ?- likes(X,Y).

X = mary
Y = tom;

X = mary
Y = bob;