Re: One possible answer to typeset vs. unset

[Felipe Contreras <felipe.contreras@xxxxxxxxx>]

Hello Bart,

Sorry about the delay, I've been busy with other projects.

I merged my approach and your approach and I'll be sending a patch to
show the resulting differences.

On Fri, Dec 4, 2020 at 6:52 PM Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx> wrote:

> On Fri, Dec 4, 2020 at 3:04 AM Felipe Contreras
> <felipe.contreras@xxxxxxxxx> wrote:
> >
> > Next, I think all the instances in which PM_UNSET is checked should be
> > verified, to see if PM_DECLAREDNULL makes sense in those. I'll do
> > that.
>
> In cases I've discovered so far, it's actually more likely that one
> has to check whether PM_UNSET and PM_DECLARED are boolean different,
> rather than whether both are (not) set.

Literally the first instance of PM_USET I checked shows a discrepancy
between my approach and your approach.

  f () {
    local var
    print ${(t)var}
  }
  f

With my approach this prints "scalar-local" (I think correctly). With
your approach it doesn't print anything.

> > And I think that's it. All that's left is deciding what flag would
> > turn this mode on.
>
> I'm leaning toward POSIXBUILTINS.

Would ksh emulation enable this flag?

> > Lastly, I don't know if there is any low-hanging fruit, for example;
> > doing the same as bash 5.0 with localvar_inherit and localvar_unset.
>
> I thoroughly dislike localvar_inherit.  I wonder if it's in bash 5.0
> just to be able to compare the suggested semantics from that rejected
> POSIX proposal we've previously discussed.  I may be biased by long
> use of the zsh semantic, but treating global -> local like environ ->
> global seems weird, unless there's also a way to "export" a local back
> to global.

After considering it further I don't think it makes sense to have this
as default.

No other language does something like that.

> > I don't quite get localvar_unset, but seems to also be a sensible default.
>
> If I'm reading the bash manual correctly, localvar_unset means that
> "unset foo" behaves like "local foo; unset foo".  Thus (Chet will
> probably correct me):

If so I don't think it makes sense to have this as default.

-- 
Felipe Contreras