or if there were a lex_local that could just be dropped in for lexicals as local can for globals.

First of all local is the wrong approach, because local just manipulates already declared pack-vars, so under strict you would be forced to predeclare your variables with "our" (or "my") in the outer scope. (look at first our in the following code) (see update)

I would love to have a lexical local in P5 BUT not with the extra magic of declaring missing variables your assuming.

What you really want is aliasing like $_[ ] variables do.

I know about *, although it doesn't seem to do much for lexicals, but what do you mean by pack-vars?

Aliasing with package-variables 

use strict;
use warnings;
$\="\n";
 
my $lamb = sub { 
  our ($d,$e); # local doesn't declare!!!
  local (*d,*e)=\(@_); 
  $d += $e ;
};
 
our $d="D";
our $u=10; 
$lamb->($u,5); 
print $u;  #> 15
print $d;  #> D

[download]

However, I don't know how to improve.

from your /msg:

What can I do to improve? I try to phrase my questions as (1) an informal description of what I want; (2) imaginary code that'll do what I want; (3) descriptions of what I've tried, and what I don't want to do (ideally, with explanations).

some ideas:

  1. Post working code which exactly does what you want, but in a "unpretty" way. e.g. with
    • $_[0] or
    • lex-refs $$x or
    • aliased pack-vars *x ...

  2. Express what you want to avoid in the working example (uglyness, doubelsigils, pack-vars,...)

  3. Post a test program which proofs every functionality you want to have covered, like
    • aliasing,
    • locality..
    4. e.g. with Test:More like in this post

  4. Write a codegenerator using eval which covers all edge cases e.g.
    • with or without use strict;,
    • with or without use warnings;,
    • variables known/unknown in outer scope,
    • outerscope vars are lex or pack

  5. Make clear which moduls are acceptable to be used...
    • None
    • Just CORE
    • CPAN w/o XS
    • CPAN
    • any

Cheers Rolf

UPDATE: as JavaFan pointed out here you are not forced to use our with full-qualified varnames, so this works 

my $lamb = sub { 
  #  our ($d,$e);
  local (*::d,*::e)=\(@_); 
  $::d += $::e ;
};

[download]
but I don't know if this meets your criteria of being more elegant than using $_[0] += $_[1] and furthermore it's only a pack-var thing, in P5 lex-vars have no namespaces...

In reply to Re^5: Local for lexicals by LanX
in thread Local for lexicals by JadeNB

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