Unset and $empty[(i)] and $empty[(I)] -- worth the effort?

Unset and $empty[(i)] and $empty[(I)] -- worth the effort?

[Bart Schaefer]

Current behavior (git master branch):

5.8.0.2-dev % print $notset[(i)] $notset[(I)]

5.8.0.2-dev % typeset emptystr
5.8.0.2-dev % print $emptystr[(i)] $emptystr[(I)]
0 0
5.8.0.2-dev % typeset -a emptyarr
5.8.0.2-dev % print $emptyarr[(i)] $emptyarr[(I)]
1 0
5.8.0.2-dev % unset emptyarr
5.8.0.2-dev % print $emptyarr[(i)] $emptyarr[(I)]

5.8.0.2-dev %

I want to rationalize $emptystr[(i)] by saying that it's searching for
an empty substring and it did find one, so it can't return
(($#emptystr + 1)), but there's not really a $emptystr[0] either.  In
the reverse direction, if an empty stubstring is allowed to match
there's no unambiguous answer for $emptystr[(I)].

Behavior on the declarednull branch:

delclarednull % print $notset[(i)] $notset[(I)]

delclarednull % typeset emptystr
delclarednull % print $emptystr[(i)] $emptystr[(I)]

delclarednull % emptystr=""
delclarednull % print $emptystr[(i)] $emptystr[(I)]
0 0
delclarednull % typeset -a emptyarr
delclarednull % print $emptyarr[(i)] $emptyarr[(I)]

delclarednull % emptyarr=()
delclarednull % print $emptyarr[(i)] $emptyarr[(I)]
1 0
delclarednull % unset emptyarr
delclarednull % print $emptyarr[(i)] $emptyarr[(I)]

delclarednull %

Given that the behavior on $emptystr is already poorly defined, I'm
not sure it makes much sense to put any effort into making the
uninitialized $emptyarr case differ from the $notset case.

Further opinions?

Re: Unset and $empty[(i)] and $empty[(I)] -- worth the effort?

[Felipe Contreras]

On Mon, Dec 7, 2020 at 5:13 PM Bart Schaefer <schaefer@brasslantern.com> wrote:

> Given that the behavior on $emptystr is already poorly defined, I'm
> not sure it makes much sense to put any effort into making the
> uninitialized $emptyarr case differ from the $notset case.

True. I misunderstood what $arr[(i|I)] did, and I can't find any
documentation about them.

But given what I can gather from the tests, it probably is not a
use-case that anybody would care deeply about, ever. If it turns out
somebody does, that can be fixed later.

That's my two cents.

Cheers.

-- 
Felipe Contreras

Re: Unset and $empty[(i)] and $empty[(I)] -- worth the effort?

[Phil Pennock]

On 2020-12-23 at 17:04 -0600, Felipe Contreras wrote:
> True. I misunderstood what $arr[(i|I)] did, and I can't find any
> documentation about them.

zshparam(1), "Subscript Flags".

It's sometimes a little confusing that most of the expansion flags are
in zshexpn(1), except these.

-Phil

Re: Unset and $empty[(i)] and $empty[(I)] -- worth the effort?

[Felipe Contreras]

On Thu, Dec 24, 2020 at 1:06 PM Phil Pennock
<zsh-workers+phil.pennock@spodhuis.org> wrote:
>
> On 2020-12-23 at 17:04 -0600, Felipe Contreras wrote:
> > True. I misunderstood what $arr[(i|I)] did, and I can't find any
> > documentation about them.
>
> zshparam(1), "Subscript Flags".
>
> It's sometimes a little confusing that most of the expansion flags are
> in zshexpn(1), except these.

Ahh, I see. Thank you.

-- 
Felipe Contreras