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|Reading dynamic data from a file|
It may seem attractive to use consult/1 for loading a file holding `case data' as Prolog facts. However, this is not a very good plan.
A much better approach is to load the file by hand. If we have dynamic data on a graph as arc/2 facts, this looks as follows.
:- use_module(library(error)). :- dynamic arc/2. load_arcs(File) :- retractall(arc(_,_)), setup_call_cleanup( open(File, read, Stream), load_arcs_from_stream(Stream), close(Stream)). load_arcs_from_stream(Stream) :- read(Stream, T0), load_arcs(T0, Stream). load_arcs(end_of_file, _) :- !. load_arcs(arc(From, To), Stream) :- !, assert(arc(From, To)), read(Stream, T2), load_arcs(T2, Stream). load_arcs(Term, _Stream) :- type_error(arc, Term).
Of course you should adapt this code to your case. This code properly handles your code as dynamic data and doesn't allow a user of your program to fool you by adding a term
arc(_, _) :- shell('format C').