Re: Jython 2.7.0 final released!

> This would take much more than a conditional grammar, we'd have to
> somehow keep two runtimes around and be able to mix them. We'd need
> things like sometimes old style classes are permitted, sometimes not

Hmmm I am honestly not 100% aware of all differences between Python 2 and 3
to consider, so please apoligize if my thoughts are too naive.
Rather than two runtimes I imagine kind of one runtime that is the
"Least common multiple" of Python 2 and 3. (Jython already delivers a runtime
that is kind of "Least common multiple" of Python 2 and Java; extending
this to Python 3 sounds almost simple compared to what has already been achieved)
E.g. for the old- vs new-style classes concern:
Python 2.7 already _has_ this mix of old- and new style classes and deciding
whether to permit old ones would be trivial due to a different import-directive.

However, if you say it can't be done (with reasonable effort), I trust you and
won't discuss further. I just wanted to make sure, the idea was considered.

Regards

Stefan


> Gesendet: Samstag, 09. Mai 2015 um 01:31 Uhr
> Von: "[email protected]" <[email protected]>
> An: "Stefan Richthofer" <[email protected]>
> Cc: "Jython Developers" <[email protected]>
> Betreff: Re: Re: [Jython-dev] Jython 2.7.0 final released!
>
> On Fri, May 8, 2015 at 5:41 AM, Stefan Richthofer
> <[email protected]> wrote:
> >>>grammar to keep 2.7 and 3.5 sort of parsing at the same time
> >
> > I had no idea this would be actually possible, but it sounds
> > very interesting. Did you consider this as an actual feature
> > for Jython3?
> What might make sense someday if I have time would be conditional
> parsing of either with the same grammar. Actually parsing at the same
> time creates terrible things (and I am perpetrating terrible things
> for now).
> 
> For example, raise_stmt in Python2 is (from CPython's Grammar) looks like:
> raise_stmt: 'raise' [test [',' test [',' test]]]
> 
> Python3's is:
> raise_stmt: 'raise' [test ['from' test]]
> 
> What I am doing would translate to:
> raise_stmt: 'raise' [test ['from'][',' test [',' test]]]
> 
> Which would allow horrors like:
> 
> raise Exception from None, foo, bar
> 
> > Did you consider this as an actual feature
> > for Jython3? Parsing 2.7 and 3.5 at the same time sounds weired,
> > but what about something like a new import directive, let's say
> > "import2" to import code that is known to be Python 2.7?
> This would take much more than a conditional grammar, we'd have to
> somehow keep two runtimes around and be able to mix them. We'd need
> things like sometimes old style classes are permitted, sometimes not,
> etc. That's definitely too hard (at least for me) and probably way too
> ugly. Although it is the sort of crazy thing that can sometimes
> interests Jim :)
> 
> -Frank
> 

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