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Python from Wise Guy's Viewpoint

Pascal Costanza costanza at web.de
Tue Oct 28 19:29:23 EST 2003 
Matthias Blume wrote:

> Pascal Costanza <costanza at web.de> writes:
> 
> 
>>Matthias Blume wrote:
>>
>>
>>>Pascal Costanza <costanza at web.de> writes:
>>
>>>>I think that Neelakantan has better examples for programs that are
>>>>possible to write with a statically typed language, but not with
>>>>dynamically typed ones. (Not 100% sure yet, though.)
>>>
>>>There are no such programs, obviously.  You can always translate a
>>
>>>statically typed program into a dynamically typed one (and vice
>>>versa).
>>
>>No, for christ's sake! There are dynamically typed programs that you
>>cannot translate into statically typed ones!
> 
> 
> Yes you can.  (In the worst case scenario you lose all the benefits of
> static typing.  But a translation is *always* possible. After all,
> dynamically typed programs are already statically typed in the trival
> "one type fits all" sense.)

No, that's not all you need to do. Essentially you would need to write a 
complete interpreter/compiler for the dynamically typed language on top 
of the statically typed one, _if_ you want runtime metaprogramming. 
That's not what I would call a straightforward translation.

But this is really getting tiring.

> [This whole discussion is entirely due to a mismatch of our notions of
> what constitutes expressive power.]

No, it's not. There's a class of programs that exhibit a certain 
behavior at runtime that you cannot write in a statically typed language 
_directly in the language itself_. There's no program that exhibits a 
certain behavior at runtime that you can only write in a statically 
typed language. [1]

That's a fact that you simply don't want to admit. But you're 
objectively wrong here.

However, the horse is beaten to death by now.


Good bye.

Pascal

[11 Except perhaps for a class of programs that would change their 
runtime and/or space complexity, provided they would need lots of 
dynamic type checks. But I haven't sorted out yet whether this class 
really exists.
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