Path: utzoo!mnetor!uunet!ncc!alberta!ubc-cs!voda
From: voda@ubc-cs (Paul Voda)
Newsgroups: comp.lang.prolog
Subject: Prolog as a "real" language
Message-ID: <1926@ubc-cs.UUCP>
Date: 4 Apr 88 15:11:59 GMT
References: <8231@agate.BERKELEY.EDU>
Sender: nobody@ubc-cs.UUCP
Reply-To: voda@ubc-cs.UUCP (Paul Voda)
Organization: UBC Department of Computer Science, Vancouver, B.C., Canada
Lines: 42
Keywords: Interpretation of PROLOG failure, Logic Programming

This is a response to the claim by E. Lagache that he prefers a practical
and dirty Prolog before a logically pure and "impractical" one.

If this outrageous claim were made by somebody else I would not bother
to polemize. Either the person is making a bad joke or else he should
not be a logic programmer. In the latter case he should use C possibly
amended by some backtracking primitives.

But since the claim was made by Lagache I think that a rebutal is
required.

The Prolog community is split into two groups.

The first group is willing to sacrifice the logic in order to attain
efficiency. These are the assert, retract, and var users who want
to have all the goodies from the procedural languages (arrays,
reassignable variables, exceptions) right now. The only thing that
matters to them is the efficiency.

The people in the second second group think that if the logic programmers
will not care about logic nobody will. Quick hacks are repulsive to them.
There are two subgroups in this group. The first subgroup
thinks that the language should not be extended but rather the
compilers must become smart enough to recognize an optimization
(for instance the automatic detection of reusable memory).
The people in this group are willing to live with the inefficiency
in the hope that the research will eventually solve the problem.

The second subgroup (I count myself here) is willing to extend
the language provided the extensions can be logically explained.
The logic is primary but if the efficiency can be obtained via
an extension I do not mind the extension.

But Lagache wants both have the cake and eat it.
He unabashedly proclaims himself to belong into the first group, yet
not so long ago he offered to the logic community his own library
of Prolog predicates. How does he think anybody will accept the
library if there is no way to logically describe the "predicates"
contained in it? Before a predicate is accepted it must have
a clear specification (declarative reading). Knowing that the author
does not care about these things (and some of the "predicates" in the
library are really badly designed) I would never contemplate using it.