Re: Papers saying Ada as an overly complex language and hard to implement

["Stanley R. Allen" <s_allen@hso.link.com>]

Yongxiang Gao wrote:
> 
> Hi, Guy
>     I put the original mail from my boss here. What are you going to say?
>     Don't show off too much.
> Thanks.
> Yongxiang
> 
>  Subject: another TA task
>     Date: Thu, 12 Feb 1998 09:14:53 -0600 (CST)
>     From: Calvin Lin <lin@cs.utexas.edu>
>       To: gyx@cs.utexas.edu
> 
> Yongxiang,
> 
>     Could you do another literature search for me?  I'm interested in
> papers that explain why Ada is an overly complex language, why it's
> a hard language to write a compiler for, and other problems with Ada.
> 
>     Thanks a lot.
> 
>                         Calvin

Ha, Ha!  This is a good one.

Perhaps some of the compiler vendors here should clarify matters
for Dr. Lin.  However, it is possible that his mind has already
snapped shut concerning this topic.

In the mean time, Yongxiang, please look at both sides of the
issue and make up your own mind.  Understand that every
language has its enemies as well as proponents.  It is not a
hard problem to find articles which say bad things about
Ada, C++, Java, Eiffel, COBOL, or any other computer
language.  Every time a new language comes out, "complexity"
is always one of the things it is criticized for, and this
includes languages whuch are explicitly designed to be
"simple" (yes, even Java has been criticized on this basis).

There common yearning among software developers for more
"simplicity", akin to the desire often expressed by people
for "simpler times" -- when life itself was supposedly not
so busy and complicated.  A related desire is for "pure"
programming languages, meaning different things to 
different people, e.g. "mathematically rigorous" (the
kind of thing Dr. Edsger Dijkstra wants), "perfectly
orthogonal" (all features independent and composable),
or "uni-visionary" (integrated around a single
concept: Smalltalk ["every feature is an object"],
purer versions of Lisp ["everything is a list"],
occam2 ["all statements are processes"]).

Academic research tends to theoretical concerns, so
it is not surprising that "pure" or "simple" languages
are rated more highly among language researchers (like
Dr. Lin) than pragmatic languages like Ada or C++.
Dr. Dijkstra, for example, is so emphatically
concerned with languages as theory-proof vehicles that
he even objects to implementing the languages!

Theoretical research in programming languages is very
valuable and has contributed considerably to the
success of Ada as a great implementation tool.
However, it is generally true that the original
languages developed for the theory or research were too
limited to be used by themselves as broadly-applicable
programming languages.  As an example, consider CSP
by Tony Hoare -- a great advance in the theory of
programming languages, and the foundation of the
occam language.  occam proved to be too restrictive
in practice, and so came occam2 -- which was still
too often limited in its breadth.  CSP did contribute
to the Ada rendevous concept, and thus some of its
legacy continues to be influential in a broader
context.  Likewise, Ada 95's "protected objects"
mechanism was influenced by research done by Andrew
Tannenbaum on the Orca programming language.

All of this does not mean that programming language
research has only one goal, to see new and better
features appear in general programming languages;
but it is definitely one of the goals of such
research.  And those general programming languages
(like Ada) which incorporate well-researched elements
will of necessity also include things like low-level
bit-oriented operations, extensive file I/O features
run-time library routines, and other features which
are generally excluded from languages used for
CS research.  All of these things "complicate" a
general programming language (though they will
often make the job of development simpler) and
make it more difficult to implement.

For a more positive perspective on the Ada
language than you may be getting from U Texas,
see these WWW pages:

http://sw-eng.falls-church.va.us/AdaIC/projects
http://www.acm.org/sigada/news/suny.html
http://www.adahome.com

-- 
Stanley Allen
mailto:s_allen@hso.link.com