Path: utzoo!attcan!uunet!munnari.oz.au!cluster!andrewt
From: andrewt@cs.su.oz (Andrew Taylor)
Newsgroups: comp.lang.prolog
Subject: Re: incrementing values
Message-ID: <704@cluster.cs.su.oz>
Date: 7 Feb 90 23:44:53 GMT
References: <17467@megaron.cs.arizona.edu> <31462@shemp.CS.UCLA.EDU> <34699@iuvax.cs.indiana.edu> <17483@megaron.cs.arizona.edu> <7926@cognos.UUCP>
Sender: news@cluster.cs.su.oz
Reply-To: andrewt@cluster.cs.su.oz (Andrew Taylor)
Organization: Basser Dept of Computer Science, University of Sydney, Australia
Lines: 28


I've thought of writing of pre-processor to effectively allow
a variable's scope to include more than one predicate.

The user would declare a "scope" indicating the predicates involved,
the entry point and the variables to be global to the scope.
There would a notation for destructive assignment to a global variable
which would be converted by the preprocessor to an assignment to
a new version of the variable. Here's an example which writes helloworld.

scope(main/0, [main/0, a/0, b/0], X).
main :- X = hello, a, write(X).
a :- b.
b :- write(X), X <- world.

/* The preprocessor would output */

main :- X0 = hello, a(X0, X), write(X).
a(X0, X) :- b(X0, X).
b(X0, X) :- write(X0), X = world.


Lately I've been writing a lot code which be much easier to read and
less tedious to write the above preprocessor was used.

Has anyone done something like this already, or think its a bad idea?

Andrew