Re: "no variable or argument declarations are necessary."

>
> I can't help but feel that a lot of people have specific typechecking
> systems in mind and then conclude that the limits of such a symtem
> are inherent in typechecking itself.

I've been writing a type-checker for my diploma thesis for a functionnal
programmming language. And it _is_ limited. The very subject of my work
was to explore extended type-checking methods (so called
multi-level-specifications),, which can be shwon to be NP-hard problems.
Which naturally limits the domains they can be used to.

> IMO a good type system doesn't need to limit python in any way.

It has to. certainly. Take alone the list implementation - while
typesystems as ML allow for generics (with much less typing overhead
than JAVA), the list is always homogenous. Which python's aren't - and
that a great thing(tm), even though ususally the contents of a list
share some common behaviour. And that exactly is the key point here: in
a statically typed world, that common behaviour must have been extracted
and made explicit. Which is the cause for that notorious java io API.
And, to extend the argument to ML-type type-checking, there you need a
disjoint union of the possible types - _beforehand_, and the code
dealing with it has to be aware of it.

In python OTH, I just pass objects I like into the list - if they
behave, fine.

DIez
Received on Sat Oct 15 04:13:11 2005