<[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
Adding Optional Static Typing to Python looks like a quite complex thing, but useful too: http://www.artima.com/weblogs/viewpost.jsp?thread=85551
One of the comments on Artima asks a rather profound question: static typing is an answer. What's the question? (That's a paraphrase.)
The answer that everyone seems to give is that it prevents errors and clarifies the program.
I'm not convinced that it's all that effective at either objective. My viewpoint on this is that of someone who generally uses test first programming (as in Test Driven Development or Extreme Programming). Many of the supposed advantages simply aren't there when you go to the discipline of writing a test and then writing exactly the code needed to make the test pass, and not one keystroke more.
Most of the kinds of error that static typing is supposed to catch simply don't persist for more than a minute when you do test driven development.
This isn't to say TDD is the be-all and end-all of correctness. Formal methods and formal inspections both have very good reputations. In fact, the technique with the best reputation is embodied in a sign that was on the wall of every office of the old IBM: Think!
So let's look a bit deeper. As far as I remember, static typing came out of the formal methods work in the '70s by people like Djikstra, Hoar and Wirth (to name only a few.) The thing is, if you properly use the formal program derivation methods they advocated, then you don't need it: your program will be as correct as it's possible to get short of your being promoted to godhood.
So the conclusion here is that static typing is an attempt to make programming safe for people that shouldn't be programming in the first place. This may sound a bit cynical, but most real uber-programmers have either Lisp or Smalltalk in their backgrounds, and frequently both one. Neither of those languages have static typing, and they simply don't need it.
So if the problem is reducing errors, then maybe we should be working on the places where errors show up.
Another point that's sometimes raised is that it's useful to provide type information via reflection. I used to think that was a valid concern until I started work on PyFit. I had to put a rather simplistic metadata facility into the program to substitute for not having type information, and I found that it was incredibly useful for other things that you can't get from reflection on type data.
John Roth
Bear hugs, bearophile
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