Re: delete of nested array is in consistent

[Peng Yu]

I feel if `delete a[“”]` can initialize the array, it should be intuitive
to support `delete a[1][“”]` as well. The definition of the language should
be separated from the difficulties in the implementation.

On Fri, Apr 17, 2020 at 8:46 AM <address@hidden> wrote:

> I poked at this in a debugger. Basically for
>
>         BEGIN { delete a[1][""]; print typeof(a[1]) }
>
> a[1] never existed as a defined array, just as a[1][""] doesn't have any
> value associated with it.  Thus the delete effectively does nothing.
>
> So, when typeof() is called on a[1], it reports undefined, since no direct
> assignment was ever made to it.
>
> Andy's suggestion:
>
>         BEGIN { a[1][""]; delete a[1][""]; print typeof(a[1]) }
>
> is the right way to go to force gawk to create a[1] and make it
> into an array.
>
> Forcing that creation from within the delete statement is way too
> hard to do, and definitely much less clear at the awk level as to
> what's going on anyway.
>
> Arnold
>
> "Andrew J. Schorr" <address@hidden> wrote:
>
> > On Fri, Apr 17, 2020 at 01:26:17AM -0600, address@hidden wrote:
> > > Peng Yu <address@hidden> wrote:
> > >
> > > > See below. I'd expect the second one should also print array. Is it
> a bug?
> > > >
> > > > $ awk -e 'BEGIN { delete a[""]; print typeof(a) }'
> > > > array
> > > > $ awk -e 'BEGIN { delete a[1][""]; print typeof(a[1]) }'
> > > > unassigned
> > > >
> > > > --
> > > > Regards,
> > > > Peng
> > >
> > > Upgrade your version of gawk:
> > >
> > > $ ./gawk --version | sed 2q
> > > GNU Awk 5.1.0, API: 3.0 (GNU MPFR 4.0.1, GNU MP 6.1.2)
> > > Copyright (C) 1989, 1991-2020 Free Software Foundation.
> > > $ ./gawk 'BEGIN { delete a[""]; print typeof(a) }'
> > > array
> > > $ ./gawk 'BEGIN { delete a[1][""]; print typeof(a) }'
> > > array
> >
> > Actually, in latest gawk, his second example still says unassigned:
> >
> > bash-4.2$ ./gawk --version | head -1
> > GNU Awk 5.1.0, API: 3.0 (GNU MPFR 3.1.1, GNU MP 6.0.0)
> > bash-4.2$ ./gawk 'BEGIN { delete a[1][""]; print typeof(a[1]) }'
> > unassigned
> >
> > This gives the desired outcome:
> > bash-4.2$ ./gawk 'BEGIN { a[1][""]; delete a[1][""]; print typeof(a[1])
> }'
> > array
> >
> > Regards,
> > Andy
>
> --
Regards,
Peng