The “does Python have variables?” debate

[Steven D'Aprano]

On Thu, 08 May 2014 12:09:21 +1000, Chris Angelico wrote:

> On Thu, May 8, 2014 at 11:27 AM, Steven D'Aprano
> <steve+comp.lang.python at pearwood.info> wrote:
>> If I have understood correctly, and I welcome confirmation or
>> correction, one can have any combination of:
>>
>> * dynamic typing and name binding (e.g. Python and Ruby); * static
>> typing and name binding (e.g. Java); * dynamic typing and
>> fixed-location variables (any examples?); * static typing and
>> fixed-location variables (C, Pascal).
> 
> Dynamic typing and fixed locations could really only be assembly
> language, I think.

Not so! That's how __slots__ and local variables work in CPython.

Objects are different sizes, so CPython can't allocate a box of a fixed 
size unless it knows how big the box needs to be. Fortunately, pointers 
are all the same size, so the object lives on the heap and the pointer 
goes in the box.

The point being, there could be a language that used fixed locations for 
variables, while still being fully dynamically typed. That would allow 
the language to use pass-by-name or pass-by-reference semantics instead 
of pass-by-value or pass-by-shared-object.




-- 
Steven