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From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: making a "call" to a text file
Message-ID: <3447@goanna.cs.rmit.oz.au>
Date: 20 Jul 90 09:09:32 GMT
References: <EIVERSON.90Jul19123922@aigyptos.nmsu.edu>
Distribution: comp
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 43

In article <EIVERSON.90Jul19123922@aigyptos.nmsu.edu>, eiverson@nmsu.edu (Eric Iverson) writes:
> I am working with a very large text file of dictionary definitions in
> Prolog format.  What I would like to do is write a routine that does a
> virtual call without actually consulting the file.

> However, while [read] works, it is far too slow for multiple queries.
> Is there something that could be implemented under grep or sed or lex
> that would do the same thing?

I'm puzzled.  If you want to get the thing into Prolog, what good is
it going to do you to use grep?

Have you tried building an index
	term_at(Term, StreamPosition).
where the Term recorded in the index is an abstraction of the term in the
file?  You might even build a multi-level index.  If the terms in the file
look like
> int(play(v,12), ...

you might build an index like
	term_at(int(X,_), Pos) :-
		term_at_int(X, Pos).
	...
	term_at_int(play(X,_), Pos) :-
		term_at_int_play(X, Pos).
	...
	term_at_int_play(v, /* the position where the term 
				int(play(v,_),_) starts in the file */).

and you would do
	term_from_file(Term) :-
		file_stream(Stream),
		term_at(Term, Pos),
		stream_position(Stream, _, Pos),
		read(Stream, Term).

you *would* have to compile the index file, but that would presumably
be rather smaller than the file as a whole.

(By the way, the example shown looked as though it was over-using lists.)
-- 
Science is all about asking the right questions.  | ok@goanna.cs.rmit.oz.au
I'm afraid you just asked one of the wrong ones.  | (quote from Playfair)