I would like to construct a mechanism that constructs different facts depending from txt file, imported in prolog. I already have found some examples where they directly assert the line that was read from the file, but I have to transform the data before assertion can take place.
To give an example:
man = {m1, m2}.
m1: w1 > w2.
should be read as:
man(m1).
man(m2).
prefer(m1, w1, 1).
prefer(m1, w2, 2).
Is it possible to construct these facts based on the symbols of the input?
thanks to the fact that data presented in example is valid Prolog syntax, this code will do
load_file_data(File) :-
open(File, read, Stream),
repeat,
read(Stream, Term),
( Term = end_of_file
-> true
; process(Term),
fail
),
close(Stream).
process(X = {L}) :-
forall(arg(_, L, A), (F =.. [X, A], assert(F))).
process(X : A > B) :-
assert(prefer(X, A, 1)),
assert(prefer(X, B, 2)).
note that the precedence of operators in m1: w1 > w2 is not what we could expect, but it works anyway, thanks to complete pattern matching. Use
?- write_canonical(m1 : w1 > w2).
>(:(m1,w1),w2)
to check precedence when not sure.