The lost Beautiful Programming Language

It was old time when a new programming language comes out, trying to be the best of all existing languages, designed by a Guru, aiming too fill a hole, etc. I think the last one was Java. Today when we see what a developer can do with an IDE like eclipse on Java, we really wonder what will the next language be and how can it be better.

However this is not taking account what mankind can do for its own loss. When we can't do better, we do worse.

The web pressure made plenty of "web" languages pop up in the landscape. One of them, Flex, looks very popular. But after playing with it, it becomes clear to me that Flex is backtracking.

Flex comes with Flex builder, a plugin on eclipse. However, the integration in eclipse is very minimal. No refactoring, no code assist, no automatic indentation, complex project settings. Only the editor, the debugger, a profiler, and the expensive wysiwyg designer that generates xml are available. I'm not sure it worths the 400M of my RAM the flex builder is eating. All in all, I miss Java support in Eclipse.

But IDE support is not all. Flex syntax is confusing, especially when it mixes xml and ActionScript. Even the semantic is misleading. Let's take an example:

  var t:Object = { foo:bar } ;

The right hand part creates an object, actually an "association list". It contains a property of type key/value, where key is "foo" and value is "bar". "foo" is a String literal, but "bar" is supposed to be an object. The value is stored in the association list, but is eventually converted to a string. To use it:

  t.foo ;
  // or
  t["foo"] ;

Note the very unusual use of "." and "[ ]". Anyway, this construct is very handy. Basically, an association list is an hashtable.


I let you imagine how much time it needs to figure out this simple feature from the documentation, and how error-prone can be a language with plenty of this kind of counter-intuitive syntax. I know, this is common with scripting language. But can we still speak about scripting languages when it has packages and an object-oriented layer?

So yes, Flex is the royal language for RIA, but no, it's not as slick as Java.

The most expensive bug

1996 june 4th, the first european rocket Ariane V exploded 40 seconds after launch. The payload alone cost about US$370 million. The cause ? A bad cast in the software initiated a chain of dramatic errors and led to Ariane destruction.

The full report worths the reading, here is a summary.

The attitude of the rocket is given by an Inertial Reference System (IRS), which is a combination of gyro lasers and accelerometers. This critical piece of hardware sends a stream of data about position, height, speed and acceleration to the main computer, which controls the exhaust pipes and drives the rocket along its expected trajectory.

Ten years ago, on Ariane III, a software function performed pre-flight checks to test alignment of the IRS. This function was no longer used on Ariane IV, but still ran during take off. You know it's easier to leave harmless code than to remove it. This function used 8 variables, 3 of them were not correctly protected although it was not an issue, because the rocket trajectory remains in range of these 3 variables.

No surprise, this function was still working on Ariane V. Unfortunately, Ariane V trajectory was a bit different and now one of the variables, the horizontal velocity, casted from 64bits float to 16bits integer, went out of range and raised an uncaught exception.

So far, no big deal. A check function raised an exception. Let's forget the check function and resume the mission.

However, the assumption on Ariane design was that software is always right and hardware may fail. The software reported an error, interpreted as the SRI was out of order. Then the SRI was shut down.

That's probably the biggest mistake. A failing unit test is embarrassing enough, but doesn't always mean the software is out of business. In this case the SRI still delivered reliable information. Unplugged, it couldn't any more.

The backup SRI started providing replacement data, and was shut down 0.05 second later, because of the same bug. Once again the assumption "hardware may fail, software not" made the backup SRI totally useless in this case.

Without sensible guidance, the rocket was doomed. But to accelerate the disaster, the SRI modules started to send stack traces instead of normal data to the main computer. The computer interpreted the data just as if the rocket was upside down and went into an emergency half turn. It started to tear apart under the physical constraints and initiated self-destruction process.

The story is sad enough like that, no need to add that a suitable test or full simulation before the flight would have found the bug.

By chance, I knew one of the member of the investigation team. He told me something not in the final report: what greatly contributed to kill Ariane V is the absence of experimented computer scientists at top management. The sofware components were simply divided and individually conducted. A competent software supervisor with suitable power could have found one of the errors, and prevented the cast exception to eventually stop the delivery of correct IRS data.

But Ariane was a physicist toy, they didn't share with a software department...

PS: The lesson was positively received. Today Ariane V is very successful and crashed only once more in 37 flights.

Marcel-Paul Schützenberger and complexity

It may happen in your lifetime that you have the luck to meet extraordinary people. MPS is one of them. I attended his lectures when I was a student at the university (Paris 7). This guy is not really famous, he didn't look for fame. We were always less than 10 in the audience. So who is he ?

MPS is a physician, a mathematician, and a computer scientist. Obviously he is excellent in all three domains. His various knowledge gives him a very realistic vision of computer science. Basically, computers were for him a tool to develop mathematics, and have a great future in biology. The last part sounds obvious today, but he said so more than 20 years ago.

But what makes him so attractive during the lectures is that he has stories to tell. As a founder of modern computer science, he met all the other founders all over the world (ok, mainly in USA), invented a very important theorem in language theory, and so he has a lot of nice anecdotes to tell about this pioneer period. I barely remember a couple of them I keep for another blog entry.

For the moment I want to focus on a sentence he said, which is carved in my brain forever:

"There are 2 kinds of program. The short ones and the long ones."

This can be understood different ways. I think the basic idea is that we should keep our distance from computer power and program complexity, and whatever we are trying to develop, after all it's only a computer program, so let's just break it down in sequence of instructions.

For example in the 80's, the hype was on Artificial Intelligence. For a majority of people AI was the most complex applications we can even think about, so much complex that nobody could complete them, btw. Eventually AI died because it didn't fulfill its promises. Some blamed computer performance, although computer power doubles every 18 months it will never catch up with AI complexity which scales up to infinity. Other blamed the poor expressivity of computer languages, too low level. That's better, but no. The real reason that killed AI is the lack of theory. Without theory, no suitable language and no proof of algorithm termination. Then your computer program can be as long as you want, it won't implement correctly the specifications (or you won't be able to prove it). Conclusion is that the program doesn't make it all by itself, it's only a tool and it won't cope with a hole in the theory.

Note that MPS didn't want to under-evaluate complexity in programming. For the developer, the complexity is relative to the constraints s/he has to deal with, about the programming language, tools, software architecture and design, and available resources. But the program is only the implementation of an algorithm, and a correct and efficient algorithm relies on a strong theory.

World Wide Web: The Boostrap Age

Back in 1990, Tim Berners-Lee started the Web with the first web server. At this time internet wasn't mainstream and I was lucky enough to work in a research institute, probably the only one in France to be connected.

At this time internet was used to send email (no spam at all), download files through ftp and read news on newsgroups.

I met several times TBL. He's a pure geek. No surprise it's major invention, the URL, has such an ugly syntax. Ugly, but functional. At least the advantage is that today everybody recognizes an URL and knows what it means, and even basic text editors turn it into an hyperlink connected to a web browser.

This URL is for me what made the WWW possible. It contains all: the protocol, the server, the server port, the document path, anchor, and query. Mixing all this in one "word" is a masterpiece. For example, when the Web is made of one server (actually the one you see in the picture), you should have a good intuition to put the IP of the server as a mandatory item of the URL. And it happens that the URL scaled up to today structure, with billions of servers and web pages...

Next major breakthrough was "mosaic", in 1993. Mosaic is yet another proof that the UI is essential. The Web as we know it today started with mosaic (which became netscape, then firefox), because it attracted people to the Web technology and started the snow ball effect of always more servers, more documents, and then more reasons to join the Web community.

Next one was alta vista search engine (1995), because Web is anarchy and it became very hard to find out something without the URL. Other search engines existed already, but Alta Vista used Scooter, a web crawler to index all reachable web pages. 10 years ago, Google swept away alta vista with the added value of Page Rank that sorts the result of a search in popular order.

No doubt that these three software milestones marked the history of the Web.