Date: Fri, 9 Dec 94 14:35:38 EST
From: conn@lear.mitre.org (Richard L. Conn)
To: team_ada@acm.org
Subject: Grady's article in Nov 94 IEEE Software

" Although C++ and Smalltalk may be winning the minds of more developers than any other language, this is not to say that all other object- oriented [he said there were over 100 earlier in the article] programming languages are inconsequential. In the category of most elegant, I place Eiffel, which has a vocal following, especially in Europe. In the most- trusted-for-complex-systems category, I place Ada. Many of the world's next-generation air-traffic-control systems are being written in Ada, for example (and as a frequent flyer, I'm very comfortable with that fact). Ada9x brings Ada fully into the object-oriented world, with the addition of inheritance with polymorphism. In the most flexible category, I place CLOS. ...
That being said, it is fairly clear that your children and your children's children will be maintaining some of the C++ and Smalltalk code that some of you are writing today. A frightening proposition, indeed, but it shows that even in an object-oriented world, some things do not change."

From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.ada
Subject: Why I like Ada
Date: 2 Dec 1994 20:44:35 +1100
Organization: Comp Sci, RMIT, Melbourne, Australia
Summary: really a whinge about a C program...

There's another formatter which I had long wanted an excuse to try. It has a lot of nice ideas. The design has been published in the technical literature; the project in question has been running for ~10 years; it's actively supported; there's a mailing list for help; and if I FTPed it the sources would be under *my* control so that nobody else would tamper with key files.

Of course, the sources are written in C. 43 *.c files. One .h file with everything in it. 25 000+ lines. Not a very big program. So I edit the Makefile to tell it where I want things put, and make one change that had not occurred to the author: I added "-Wall" to the gcc command line. OW! After about two weeks of spare time tweaking (putting 'static' here 'void' there, a prototype in the other place, really minor stuff) I finally have it to the point where there are about 300 lines of output from Lint (that is a huge improvement, let me tell you).

Fairly obvious point number 1: about 100 of those lines warn that the ANSI C rules for mixed signed/unsigned arithmetic are DIFFERENT from the traditional K&R/pcc/UNIX rules for mixed signed/unsigned arithmetic, and that this may have affected line so-and-so. I have no idea how many of the warnings are genuine, BUT THE AUTHOR WASN'T SEEING ANY OF THEM because he wasn't using gcc -Wall or lint.

Interestingly enough, while I was composing this message I decided to try to do something about those 100 lines. It turns out that *most* of them are benign (lint warning that "x > 0" is suspicious) but lurking amongst them are

• several where a group of variables having the same *abstract* type (count-of ) have been given different *concrete* types (some int, some unsigned char, some unsigned short &c)

• a couple of places where potentially serious range problems were lurking (e.g. a count being stored in an unsigned char, with not even a comment in the code to ensure that there are at most 255 things to count, and some reason to suspect there might be more)

• code that doesn't make sense unless 'int' is exactly 32 bits.

• the C tools (gcc -Wall and lint) *can* find some dangerous things,
• the normal sloppiness of the compiler means that the original author was encouraged to develop a style in which genuine warnings (had he ever asked for them) would have been swamped
• I am getting *extremely* nervous about this program; there is NO connection in the code between the bounds of the many ranges and the declared concrete types of the variables.
• The Ada approach of having lots of integer subtypes is clearly the right thing for this program.

	p = ...
	while (...) {
	    x = ...
	    ...
	}
	... use x ...

When I got most of the warnings caused by sloppy style out of the way, I found that a number of serious and potentially serious problems were present, and gcc -Wall and lint found them.

1. There is a really weird statement: (p = chpt) - 1;

2. There is a data type with range at least 0..520. The values were being stored in unsigned char (0..255)! Type a long enough word at this document processor, and BOOM! There is very good reason to believe that this is not the only wrong-size-for-range problem. Unfortunately, because the C code uses unsigned types, it is "well-defined"; Procrustes rules!

3. When it read a certain file, it was ALWAYS ignoring the result status of getc(). When it wrote that file (and others) it was ALWAYS ignoring the result status of putc() and friends. I have lost enough data due to stupid utilities thinking that writes can never go wrong to be really annoyed about this.

1. Ada simply would not allow this.
2. Ada lets you express the range you want, and have it checked.
3. Say what you like about TextIO, exception handling is easier to get right than dozens of if (... == -1) ... tests.

--
"The complex-type shall be a simple-type."  ISO 10206:1991 (Extended Pascal)
Richard A. O'Keefe; http://www.cs.rmit.edu.au/~ok; RMIT Comp.Sci.

From: rosen@enst.fr (Jean-Pierre Rosen)
Newsgroups: comp.lang.ada
Subject: Astree project
Date: 10 Oct 1994 08:54:41 +0100
Organization: Ecole Nationale Superieure des Telecommunications,
              Paris France

There was initially a debate about using Ada, but eventually it was decided to develop an initial prototype version in C.

After developping 300 000 lines of C code, the prototype was found so unmaintainable that the decision was taken to throw everything away and to start over - in Ada.

Ada fans are requested to refrain from smiling until the project is (succesfully) completed. :-)

From: Magnus.Kempe@di.epfl.ch (Magnus Kempe)
Newsgroups: comp.lang.ada
Subject: Re: Recommendations on software RFP/RFQs???
Date: 23 Sep 1994 08:34:00 GMT
Organization: Ecole Polytechnique Federale de Lausanne

: My organization has decided to standardize on C and C++ ...

[...]

Ignorance can only be defeated by education. The Ada awareness campaign should also target the companies who want to "standardize". By the end of this year,

Ada WILL BE THE FIRST STANDARDIZED OBJECT-ORIENTED LANGUAGE

C++ may become a standard by 1996, but it is unlikely that Borland and Microsoft will ever conform *entirely* to it; that would be out of character for these companies.

--
Magnus Kempe            "I know not what course others may take, but as for me,
Magnus.Kempe@di.epfl.ch  Give me Liberty... or give me Death!" -- Patrick Henry

From: eachus@spectre.mitre.org (Robert I. Eachus)
Newsgroups: comp.lang.ada
Subject: Re: Ada ad in Embedded Systems Programming stinks
Date: 6 Sep 94 09:40:18
Organization: The Mitre Corp., Bedford, MA.

Now I understand why languages are religions. Listening to an Ada person describe C is like listening to a Christian describe Hinduism. Remember, C is a language, not an environment. If want to impose discipline on your C code, then find a tool that supports your religion. If you allow warnings to stay in your code, then you are indeed in need of disciplining, try C++ :)

pragma SERMON(ON);

If someone tried to sell you a car with no brakes, with the explanation that drivers with good eyesight and coordination didn't often use them, you might be tempted to do physical harm to the seller. But if yhe only automobiles on the market had no brakes, no emergency flashers, no seatbelts, and no airbags, you might not be willing to "pay the extra cost" for this unwanted feature in a new car. Those who want to use the highways, but find the risk from other drivers in brakeless cars unacceptable, just throw up their hands when the drivers who have never learned to use brakes explain why they don't want them.

Lest this seem too farfetched, read the history of George Westinghouse and his "automatic" brakes for railroad cars. (Yes, once upon a time the job of the railroad brakeman was to go from car to car manually adjusting the brakes.) Or better yet, the fight by WWI fighter pilots to be permitted to carry parachutes!

If you accept the need for tools which detect and prevent major debugging problems before they occur, then you can begin to understand why software engineers are such Ada advocates. For example, while C++ designers are just beginning to understand elaboration issues, it has been at least a year since I had to help an Ada programmer who had elaboration order problems. Ada users quickly learn which structures can cause elaboration issues, use those structures only where necessary, and track the elaboration order when it may be a problem. Not painting yourself into a corner early in the design process can save months later in the development process, usually during integration.

Passing an object instead of a pointer to it (the earlier example) is a difference between Ada and C. But it is the tip of the iceburg which most C programmers never see, even after their ship (or project) sinks beneath the waves. I will continue to react rudely to any C programmer who tells me why he doesn't need compile time checking, just as I would to a driver explaining why his car has no brakes. I have had to deal with too many bodies from the (software development) highway to do otherwise.

pragma SERMON(OFF);
--
                                        Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...

Extracted from: ftp://ajpo.sei.cmu.edu/public/news/adatoday.txt
DATELINE:  July 13, 1994

Ada has numerous properties which make it a natural choice for the development of safety critical systems.

• Ada is an ANSI and ISO standard - It is well-defined and stable, and provides a portable foundation for the development of supporting tools and libraries.

• Ada supports Object Oriented Design - It provides comprehensive support for abstraction and the reuse of tested components.

• Ada has a legible style - It promotes the satisfactory execution of certification steps, including peer review and walkthroughs, and simplifies maintenance tasks.

• Ada has a coherent, modular construction - Separate compilation facilities enable the application to be written as a set of units with interface specifications and dependencies clearly exposed, enabling the organized construction of a program from trusted components.

• Ada aids the detection of errors - Strong typing facilities ensure that most errors are detected statically by the compiler, and most remaining errors are automatically detected at execution.

• Ada limits the features used by a program unit - It exposes areas where potentially unsafe features may be used and allows special treatment and testing to ensure that the safety of the program as a whole is not compromised.

[Source: "Safety Critical Software - The Ada Solution."
 Alsys world Dialogue, Spring 1994, Vol.8, Number 1.]

Newsgroups: comp.lang.ada
From: breland@photon.mcc.com (Mark A. Breland)
Subject: Re: Ada Success Stories
Date: Wed, 13 Jul 1994 22:21:30 GMT

"Those who swear by their systems choose their language carefully."

[nice, robotic auto manufacturing picture here (lotsa sparks flying)]

"In today's highly competitive commercial marketplace, system errors can be catastrophic. That's one reason why Ada has become the language of choice for developers of large, complex applications worldwide."

"Ada has the tools to find mistakes. The language;s inherent readability ensures that an error is easily understood, and is therefore quickly rectified. What's more, the compilers will stop, rather than allow incorrect code to go through. And program parts that you know to function correctly can safely be re-used. Think of the money you save by catching errors early, fixing them easily, and re-using what you know works."

"For a free kit containing a catalog of industry resources, some information on commercial Ada usage that may surprise you, and a summary of how Ada is evolving for the future, call the Ada Software Alliance at 800 380-4ADA."

"Ada. The language for a fail-safe world."

Mention is also made of TRI-Ada '94 in a small blurb at the bottom.

Now what better way to get the attention of these top 100 software purveyors than to stick an ad like this right in the middle of their shining, publicized glory?

Mark A. Breland
Microelectronics and Computer Technology Corporation (MCC)
Information Systems Division            | voice:    (512) 338-3509
3500 West Balcones Center Drive         | FAX:      (512) 338-3900
Austin, Texas 78759-6509   USA    NB#51 | internet: breland@mcc.com

From: Dale Stanbrough, RMIT, Melbourne, Australia, dale@rmit.edu.au

GNU Ada 94 (GNAT) => the best $0 you'll ever spend.
Available for DOS, Linux, OS/2, Sun Sparc, Sun Solaris, ...
Coming to a GNU supported platform near you soon...

From: David Weller, dweller@Starbase.NeoSoft.COM

Tech Journalists Compare Ada 9X vs. C++: Ada 9X: 3 , C++: 0.
For all sorts of interesting Ada 9X tidbits, run the command: "finger dweller@starbase.neosoft.com | more" (or e-mail with "finger" as subject).
"Quitting C++ isn't so difficult, provided you show as much persistence stopping as you did starting."