[Python-ideas] Null coalescing operator

[Guido van Rossum]

Obviously the AST needs to be changed. How? I dunno. Sounds like you have
some ideas. :-)

On Mon, Oct 31, 2016 at 2:44 PM, Random832 <random832 at fastmail.com> wrote:

> On Mon, Oct 31, 2016, at 13:16, Guido van Rossum wrote:
> > For "everything to the right" it would seem we have some freedom: e.g.
> > if we have "foo.bar?.baz(bletch)" is the call included? The answer is
> > yes -- the concept we're after here is named "trailer" in the Grammar
> > file in the source code (
> > https://github.com/python/cpython/blob/master/Grammar/Grammar#L119),
> > and "primary" in the reference manual (
> > https://docs.python.org/3/reference/expressions.html#primaries). This
> > means all attribute references ("x.y"), index/slice operations
> > ("x[...]"), and calls ("x(...)").
>
> One thing that I think I touched on in an earlier iteration of this
> discussion but hasn't been revisited is: what's the AST going to look
> like?
>
> Right now, foo.bar.baz(bletch) is Call(Attribute(Attribute(Name('foo'),
> 'bar'), 'baz'), [Name('bletch')])), which is identical to
> (foo.bar).baz(bletch) or (foo.bar.baz)(bletch). These are treated,
> essentially, as postfix operators, where you can parenthesize any left
> part of the expression and leave its meaning [and its AST] unchanged.
>
> Is the AST going to be unchanged, leading to the conclusion that the
> short-circuiting in (foo?.bar).baz will "reach outside of" the
> parentheses, and relying on the fact that wanting to do that with None
> is a silly thing to do in almost all cases? Or is there going to be a
> new kind of AST that is sequential rather than recursive in how it
> represents trailer/primary expressions?
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-- 
--Guido van Rossum (python.org/~guido)
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