Appending facts into an existing prolog file.
- by vuj
Hi,
I'm having trouble inserting facts into an existing prolog file, without overwriting the original contents.
Suppose I have a file test.pl:
:- dynamic born/2.
born(john,london).
born(tim,manchester).
If I load this in prolog, and I assert more facts:
| ?- assert(born(laura,kent)).
yes
I'm aware I can save this by doing:
|?- tell('test.pl'),listing(born/2),told.
Which works but test.pl now only contains the facts, not the ":- dynamic born/2":
born(john,london).
born(tim,manchester).
born(laura,kent).
This is problematic because if I reload this file, I won't be able to insert anymore facts into test.pl because ":- dynamic born/2." doesn't exist anymore.
I read somewhere that, I could do:
append('test.pl'),listing(born/2),told.
which should just append to the end of the file, however, I get the following error:
! Existence error in user:append/1
! procedure user:append/1 does not exist
! goal: user:append('test.pl')
Btw, I'm using Sicstus prolog. Does this make a difference?
Thanks!
