Reading a file in prolog [duplicate]

Answer 1

You say you want to tokenize the input - the best way to do this are definite clause grammars (DCGs). With library(pio) in SWI you can use the grammar directly to read in a file like so:

?- use_module(library(pio)).
?- phrase_from_file(seq(Xs),f).

seq([]) --> [].
seq([E|Es]) --> [E], seq(Es).

Replace now seq//1 by some more elaborate tokenizer.