Hi

I didn't expect that it's possible to dynamically access a lexical var by using eval within a closure-function (here "getset()"), but indeed it's possible.

There is no real need for this in Perl¹ ... but I wanted to share the insight I got! :)

#   Eval in Closure
#   Accessing lexical by name?
#
  
use strict;
 
sub alert {
  print @_,"\n";
}
;
my $getset;
 
my $change =sub {
  my $it=shift;
  $getset->($it,"post");
};
    
 
my $x="global";
my $test=sub {
  my $x="pre";
   
  $getset=sub  {
    my ($name,$val)=@_;
    eval('$'.$name."='".$val."'"); # I can access any variable in this
+ scope
  };
   
  alert($x);           # pre
  $change->("x");
  alert($x);           # post
}
   
;
$test->();
alert($x);             # global

[download]

The motivation for this code is that in JS one can't pass simple data-types (i.e. "scalars") by reference one need to use objects instead.

But when converting Perl-code to JS one can't control potential aliasing/referencing of parameters, e.g. a called sub could assigning to $_[].

This functional pattern could be used as workaround, and works in both languages.

Cheers Rolf

¹) Hmm ...maybe as generic accessor method in OOP...

In reply to Accessing lexicals in other scopes dynamically by name by LanX

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