Puzzled by "is"

[Trent Mick]

Dick Moores wrote:
> At 06:13 PM 8/9/2007, Ben Finney wrote:
>> It's important to also realise that the language is *deliberately*
>> non-committal on whether any given value will have this behaviour;
>> that is, it's entirely left to the language implementation which
>> optimisation trade-offs to make, and the language user (that's you and
>> I) should *not* expect any particular behaviour to hold between
>> different implementations.
> 
> I'm not clear on the meaning of "implementations" 
> here.  Would 2.5 for Windows, Mac, Linux all be 
> different implementations? Would Iron Python be another? ActivePython?

(Note that I'm jumping into this without having read the thread, so 
apologies if I didn't grasp the question in its proper context.)

Separate Python "implementations" generally refers to a separate source 
code base for that Python build. According to that definition, current 
examples of Python implementations are: CPython (from python.org, 
C-based), Jython (Java-based), Stackless Python (I'm not that familiar 
to how much of the CPython source code, if any, Stackless borrows), 
IronPython (.NET/C#-based), possibly PyPy (Python-based, I'm not that 
familiar with it). Also eventually interesting might be the recently 
announced IronMonkey (http://wiki.mozilla.org/Tamarin:IronMonkey).

Windows, Mac, Linux, etc. installations/builds/installers of a 
particular implementation would be different platform *builds* (my 
language).

ActivePython is a separate (from python.org's) *distribution* of CPython 
-- i.e. the sample implementation as CPython (same source code). This is 
similar, in some respects, to SuSE, Debian, RedHat, Ubuntu, etc. being 
different distributions of Linux.


Trent

-- 
Trent Mick
trentm at activestate.com