Ugh. It is becoming gradually clear to me that obj[] should be a syntax
error. We should definitely not indulge in obj[-] or {-}.
On Mon, Aug 17, 2020 at 11:41 AM Jonathan Fine <jfine2...@gmail.com> wrote:
> Here's a few words on whether we should allow and whether we can forbid:
> >>> something[]
>
> First, in
> >>> something[x=1]
> what I call the argv is empty, as it is with
> >>> something[]
>
> If we represent an empty argv by passing the empty tuple () to
> __getitem__, then how are
> >>> something[(), x=1]
> >>> something[x=1]
> to be distinguished from each other? Or perhaps they shouldn't be.
>
> Next, if
> >>> something[*argv]
> is allowed, then what was a syntax error becomes a run-time error. Put
> another way, an optimising compiler might want to raise syntax error for
> >>> something[*()]
> although I think that would be wrong. Compare with
> >>> 1 if True else 1 / 0
> 1
> as its possible that something[*()] won't be called.
>
> Finally, even if we forbid
> >>> something[*argv]
> in order to prevent the empty key, the door is still open. We can use
> >>> something[**dict()]
> to access something with the empty key (assuming ** arguments are allowed).
>
> And one more thing. There's rightly a strong association between [] and an
> empty list literal. To my mind, this makes
> >>> d[]
> look very odd. We're expecting something, but there's nothing there.
> Perhaps
> >>> d[-]
> would work better for signifying an empty key. Here, '[-]' is a special
> syntactic token.
>
> Aside: Consistent with this, we could use
> >>> {-}
> for the empty set literal. At present the closest we can do for an empty
> set literal is
> >>> {0} - {0}
> set()
>
> I hope all this helps.
>
> --
> Jonathan
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--
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*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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