On Apr 20, 2020, at 01:06, M.-A. Lemburg <m...@egenix.com> wrote:
>
> The current version already strikes me as way too complex.
> It's by far the most complex piece of grammar we have in Python:
>
> funcdef: 'def' NAME parameters ['->' test] ':' [TYPE_COMMENT]
> func_body_suite
But nobody’s proposing changing the function definition syntax here, only the
function call syntax. Which is a lot less hairy. It is still somewhat hairy,
but nowhere near as bad, so this argument doesn’t really apply.
Also, you’re lumping all the different proposals here, but they don’t all have
the same effect, which makes the argument even weaker.
Adding a ** mode switch does make calls significantly more complicated, because
it effectively clones half of the call grammar to switch to a similar but new
grammar.
But allowing keyword= is a simple and local change to one small subpart of the
call grammar that I don’t think adds too much burden.
And ::value in dict displays doesn’t touch the call syntax at all; it makes
only a trivial and local change to a subpart of the much simpler dict display
grammar.
And **{a,b,c} is by far the most complicated, but the complicated part isn’t in
calls (which would just gain one simple alternation); it’s in cloning half of
the expression grammar to create a new nonset_expression node; the change to
call syntax to use that new node is simple. (I’m assuming this proposal would
make **{set display} in a call a syntax error when it’s not a magic
set-of-identifiers unpacking, because otherwise I don’t know how you could
disambiguate at all.)
So, even if you hadn’t mixed up definitions and calls, I don’t think this
argument really holds much water.
I think your point that “hard to parse means hard to reason about” is a good
one, however. That’s part of my rationale for the ::value syntax in dict
displays: it’s a simple change to a simple piece of syntax that’s well isolated
and consistent everywhere it appears. But I don’t think people would actually
have a problem learning, internalizing, and reading keyword= syntax. And I
think it may be an argument against the **{a,b,c} syntax, but only in a more
subtle way than you’re advancing—people wouldn’t even internalize the right
grammar; they’d just think of it as a special use of set displays (in fact
Steven, who proposed it, encourages that reading), which is an extra special
case to learn. Which can still be acceptable (lots of people get away with
thinking of target lists as a special use of tuple displays…); it’s just a
really high bar to clear.
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/JNENJWUEORPQ6UMMTWQPMKAZUBDE37B3/
Code of Conduct: http://python.org/psf/codeofconduct/
