Static typing

[Dirk Thierbach]

Pascal Costanza <costanza at web.de> wrote:
> Unless the static type system takes away the expressive power that I need.

Even within a static type system, you can always revert to "dynamic
typing" by introducing a sufficiently universal datatype (say,
s-expressions).

Usually the need for real runtime flexiblity is quite localized (but
of course this depends of the application). Unless you really need runtime
flexibility nearly everywhere (and I cannot think of an example where
this is the case), the universal datatype approach works quite well
(though you loose the advantages of static typing in these places, of
course, and you have to compensate with more unit tests).

> I have given reasons when not to use a static type system in this 
> thread. 

Nobody forces you to use a static type system. Languages, with their
associated type systems, are *tools*, and not religions. You use
what is best for the job.

But it's a bit stupid to frown upon everything else but one's favorite
way of doing things. There are other ways. They may work a bit
differently, and it might be not obvious how to do it if you're used
to doing it differently, but that doesn't mean other ways are
completely stupid. And you might actually learn something once
you know how to do it both ways :-)

> Please take a look at the Smalltalk MOP or the CLOS MOP and tell 
> me what a static type system should look like for these languages!

You cannot take an arbitrary language and attach a good static type
system to it. Type inference will be much to difficult, for example.
There's a fine balance between language design and a good type system
that works well with it.

If you want to use Smalltalk or CLOS with dynamic typing and unit
tests, use them. If you want to use Haskell or OCaml with static typing
and type inference, use them. None is really "better" than the other.
Both have their advantages and disadvantages. But don't dismiss
one of them just because you don't know better.

- Dirk