:- object(reverse).
:- info([
version is 1.0,
author is 'Paulo Moura',
date is 2004/2/16,
comment is 'Reads and writes a simple table of facts from and to files for testing operator handling code.']).
:- op(500, xfx, next). % local object operators, not visible outside this object
:- op(500, xfx, previous).
:- initialization(reverse_file).
reverse_file :-
open('next.txt', read, RStream),
open('previous.txt', write, WStream),
read(RStream, Term), % local operators are used when reading terms ...
process(Term, RStream, WStream).
process(end_of_file, RStream, WStream) :-
close(RStream),
close(WStream).
process(X next Y, RStream, WStream) :-
write(WStream, Y previous X), % ... and when writing terms
write(WStream, '.'), nl(WStream),
read(RStream, Next),
process(Next, RStream, WStream).
:- end_object.
