On 7/9/2010 4:26 PM, Mark Dickinson wrote:
On Fri, Jul 9, 2010 at 8:37 PM, Dino Viehland<di...@microsoft.com> wrote:
Terry wrote:
This violates the important principle that allowed def and call arg
sequences should match to the extent sensible and possible. In this
sense, the SyntaxError is a bug. So I would fix this now for 3.2 and
notify the other implementors.
+1 on fixing it - trailing commas are awesome. I'm always annoyed in
C# where I frequently can't use them. This seems like a bug fix level
change that should be easy for the other implementations to fix.
Thanks for all the feedback.
If the grammar is changed to allow "def f(*, a,): pass", that still
leaves some more open questions: which of the following should be
valid?
(1) def f(*args,): pass
(2) def f(**kwargs,): pass
(3) def f(*,): pass
I would follow the same principle of making def and call match. Currently
>>> def f(*args,): pass
SyntaxError: invalid syntax
>>> def f(*args): pass
>>> f(*(1,2,3),)
SyntaxError: invalid syntax
Giving the call doc "A trailing comma may be present after the
positional and keyword arguments but does not affect the semantics.", I
was not really expecting the second syntax error. Same behavior for f(**k,).
So if you allow the definition, allow the call too.
Just for the sake of simplicity it would seem to make sense allow all
these, even if there's no obvious immediate use; for me, it keeps the
mental footprint of the language small---I don't have to remember when
the comma is or isn't allowed.
Agreed.
--
Terry Jan Reedy
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