[Python-ideas] Null coalescing operators

[MRAB]

On 2015-09-21 17:29, Stephen J. Turnbull wrote:
> Andrew Barnert writes:
>   > On Sep 21, 2015, at 01:48, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>   >
>   > >>>>> retries = default else cls.DEFAULT
>   > >
>   > > I kinda like this if-less else syntax for the symmetry with else-less
>   > > if.
>   >
>   > How do you parse this:
>   >
>   >     a if b else c else d
>   >
>   > Feel free to answer either as a human reader or as CPython's LL(1)
>   > parser.
>
> I don't know what an LL(1) parser could do offhand.  As a human, I
> would parse that greedily as (a if b else c) else d.
>
'else' is being used like 'or', except when it belongs to 'if'.

I can't see a way of handling that.

It would result in a syntax error.

> But the point's actually moot, as I'm -1 on the "??" operator in any
> form in favor of the explicit "a if a is not None else b" existing
> syntax.  And to be honest, the fact that a truly symmetric "if-less
> else" would have "or" semantics, not "??" semantics, bothers me more
> than the technical issue of whether anybody could actually parse it.
>