I was wondering, I am aware you can use assert to add facts or rules or whatever if you have declared the predicate to be -:dynamic, but this only allows the changes that are made to be kept in that session only, e.g. if you close the Prolog window then the database changes are lost.
So I was wondering, is there any way of making it so that the assert and retract predicates can make permanent changes to the Prolog .pl file?
Thanks
Answer
I can suggest you a very simple way of doing this.
1 ?- assert(a(1)).
true.
2 ?- assert(a(2)).
true.
3 ?- assert(a(3)).
true.
4 ?- a(A).
A = 1 ;
A = 2 ;
A = 3.
5 ?- tell('a_db.txt'), listing(a), told.
true.
Then close session, reopen.
1 ?- a(A).
ERROR: toplevel: Undefined procedure: a/1 (DWIM could not correct goal)
2 ?- ['a_db.txt'].
% a_db.txt compiled 0.00 sec, 516 bytes
true.
3 ?- a(A).
A = 1 ;
A = 2 ;
A = 3.
4 ?- listing(a).
:- dynamic a/1.
a(1).
a(2).
a(3).
true.