Hi

I'm a little surprised by the following behavior, I'm chaining generators, such that iterators can be combined:

my $call=0;
 
sub generator (;$) {
  my $inner_iter=shift;
  my $dummy;
  
  $outer_iter=sub {};
  # $outer_iter=sub { $inner_iter->() };
  # $outer_iter=sub { $dummy++ };
  $call++;
  
  print "Call Nr $call\n";
  
  if ($inner_iter){
    print $inner_iter."\n";
    if ( $inner_iter eq $outer_iter) {
      print "ERROR !!!\n"
    }
  }
  
  return $outer_iter;
}
 
print generator generator;

[download]

I expected that the second anonymous sub $outer_iter to be different from the first, which is also present in the same scope as $inner_iter and hasn't been destroyed yet.

But that's not the case: 

/usr/bin/perl -w /tmp/tst.pl 
Call Nr 1
Call Nr 2
CODE(0x90fa080)
ERROR !!!
CODE(0x90fa080)

[download]

Only uncommenting line 8 or 9 helps, such that an outer variable belongs to the closure of $outer_iter.

Call Nr 1
Call Nr 2
CODE(0x9604880)
CODE(0x9623210)

[download]

Seems to be an optimization from Perl, kind of constant folding of subs which aren't closures.

So I already have a work around ...

... but out of curiosity, is there any other way to force the creation of a really different instance of a sub, even with the same body but without creating a closure?

Cheers Rolf

UPDATE: I'm still not sure if this should be considered a feature or a bug. It's not the same as with other "data" structures: 
sub gen_arr {
  my $inner_arr=shift;
  
  print my $outer_arr=[];
  
  return $outer_arr;
}

gen_arr gen_arr;

#prints ARRAY(0xa179880)ARRAY(0xa179760)

[download]

In reply to Avoiding reference of sub optimization by LanX

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