Re: RFC 106 (v1) Yet another lexical variable proposal: lexical variables made default

Nate the prolific Perl6 RFC producer and commentator wrote:
> I don't think suggesting that we eliminate globals altogether is a good
> or feasible idea. It's an unnecessary crutch. They are useful in many
> circumstances.

  So here's my order of preference:

1) Eliminate dynamic variables entirely.

2) Eliminate dynamic variables from default Perl, but allow their use
with a pragma.

3) Provide a new strict pragma to disable dynamic variables.  (Note
that I have an ulterior motive, here; strict is the de-facto standard
for module writing.  If I get this into strict, then everybody will
feel obligated to write their modules in this style. :)  Of course,
module writers are supposed to be good enough to not use unnecessary
crutches, right?)

CONTEXT ALERT:  All of this is still optional to RFC 106, which can
provide for making lexical variables the default without having to do
anything to dynamic variables.  Don't have a cow if you were worried
about that.

> I think this is shaping up to be a really good proposal. Here's what I
> hear:
>
>   1. All variables are liberally lexically scoped by
>      default. Either scope them package-wide or do the
>      nearest block idea.
>
>   2. You can explicitly scope variables with my or our.
>
>   3. Global variables can still be declared with 'use vars'.
>
>   4. Dynamic keywords (like local) still only work on
>      global variables.
>
> Sound accurate?

  Everything except #4.  I explicitly believe in allowing dynamic
assignment on lexical variables.  Way back before this list, when the
first version of RFC 6 came out, Tom Christiansen commented, "One
could even make Chip happy and allow one to C<scopetemp> [one of many
proposed new names for local()] a lexical."  I'm not saying Tom was
behind the idea, but it is a possibility, and I'm behind it.
Apparently, Chip (the same one who started Topaz, I presume?) was,
too, at some earlier point in Perl history.

> Exactly how point #1 is implemented can be left till
> later, just as long as this:
>
>    $x = 1;
>    {
>       $y = $x + 1;
>    }
>    print "$y";
>
> Works without any predeclarations.

  Agreed.  Implementation suggestions (both of them) will be relegated
to the implementation section.

> P.S. I meant "package-wide" in the previous email. The package should
> always be the outermost logical container, I think.

  But packages can span multiple files.  This boogers up lexical
scoping.  Two different files should both be able to plop
subroutines/methods (and, yes, dynamic variables if they still exist)
into a package, but they need to depend upon their _lexical_ variables
not clashing.  Otherwise, some of the more esoteric Perl modules might
not be able to function (those that deliberately tweak the contents of
other packages).


J. David