Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!ncar!noao!arizona!gudeman
From: gudeman@cs.arizona.edu (David Gudeman)
Newsgroups: comp.lang.misc
Subject: Re: Need reference for "firewall" modularization
Message-ID: <26865@megaron.cs.arizona.edu>
Date: 26 Oct 90 19:06:09 GMT
Organization: U of Arizona CS Dept, Tucson
Lines: 37

In article  <961@skye.cs.ed.ac.uk> nick@cs.edinburgh.ac.uk (Nick Rothwell) writes:
]In article <1990Oct25.193935.375@arnor.uucp>, strom@arnor.uucp writes:
]> many program bugs are the result of issuing otherwise correct operations
]> *in the wrong order*

]Just a minor point here - that's a fault with conventional procedural
]languages with assignable variables, and nothing to do with typechecking.
]Functional and logic languages don't have this problem at all.

First, some functional languages and the only well-known logic
language (Prolog) certainly _do_ have this problem.  If you do things
in the wrong order, you may get peculiar results like non-termination.

Second, the implication that this would show some sort of superiority
for non-procedural languages is just wrong.  I could just as well say
"most problems in functional programs are caused by composing the
right functions in the wrong ways -- procedural languages don't have
this problem since you can't compose functions."  or "most problems in
logic languages are caused by unifying otherwise correct terms with
the wrong variables -- procedural languages don't have this problem
since they don't have unification".

Basically someone screwed-up somewhere, and changing the paradigm
just changes the nature of the screw-ups, not the quantity or the
quality.  This is not to say that changing the language itself can't
reduce errors, just that there is no reason to assume that functional
or logic languages by the fact of being function-based or predicate
logic-based reduce errors.  To be sure, functional and logic languages
tend to be higher-level than procedural languages, and higher-level
languages seem to reduce errors, but this matter of semantic level is
independent of whether the language is based on functions, predicates,
procedures, or some combination of the above.
-- 
					David Gudeman
Department of Computer Science
The University of Arizona        gudeman@cs.arizona.edu
Tucson, AZ 85721                 noao!arizona!gudeman