[Python-Dev] Pre-PEP: Task-local variables

[Phillip J. Eby]

At 04:04 PM 10/20/2005 -0400, Jeremy Hylton wrote:
>On 10/20/05, Guido van Rossum <guido at python.org> wrote:
> > Whoa, folks! Can I ask the gentlemen to curb their enthusiasm?
> >
> > PEP 343 is still (back) on the drawing table, PEP 342 has barely been
> > implemented (did it survive the AST-branch merge?), and already you
> > are talking about adding more stuff. Please put on the brakes!
>
>Yes.  PEP 342 survived the merge of the AST branch.  I wonder, though,
>if the Grammar for it can be simplified at all.  I haven't read the
>PEP closely, but I found the changes a little hard to follow.  That
>is, why was the grammar changed the way it was -- or how would you
>describe the intent of the changes?

The intent was to make it so that '(yield optional_expr)' always works, and 
also that   [lvalue =] yield optional_expr works.  If you can find another 
way to hack the grammar so that both of 'em work, it's certainly okay by 
me.  The changes I made were just the simplest things I could figure out to do.

I seem to recall that the hard part was the need for 'yield expr,expr' to 
be interpreted as '(yield expr,expr)', not '(yield expr),expr', for 
backward compatibility reasons.