On Wed, Apr 29, 2015 at 3:46 PM, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> Yury Selivanov wrote: > >> I'm not sure >> why Greg is pushing his Grammar idea so aggressively. >> > > Because I believe that any extra complexity in the grammar > needs a very strong justification. It's complexity in the > core language, like a new keyword, so it puts a burden on > everyone's brain. > > Saying "I don't think anyone would ever need to write this, > therefore we should disallow it" is not enough, given that > there is a substantial cost to disallowing it. > > If you don't think there's a cost, consider that we *both* > seem to be having trouble predicting the consequences of > your proposed syntax, and you're the one who invented it. > That's not a good sign! > I have a slightly different view. A bunch of things *must* work, e.g. f(await g(), await h()) or with await f(): (there's a longer list in the PEP). Other things may be ambiguous to most readers, e.g. what does await f() + g() mean, or can we say await await f(), and the solution is to recommend adding parentheses that make things clear to the parser *and* humans. Yury's proposal satisfies my requirements, and if we really find some unpleasant edge case we can fix it during the 3.5 release (the PEP will be provisional). -- --Guido van Rossum (python.org/~guido)
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