p5pRT
commented
12 years ago From goldstei@ugcs.caltech.edu
Created by goldstei@ugcs.caltech.edu
I've noticed that Data::Dumper does not always create ouput that will eval correctly for self-referential structures\, even if Purity=1.
For example\, take this code:
==================== use Data::Dumper;
my $h = {b => 1}; my $m = {c => $h}; $h->{d} = $m; $h->{a}[0] = $m; $Data::Dumper::Purity = 1; print Dumper($h) . "\n"; my $s = Dumper($h); my $a = eval $s; print Dumper($a);
This produces the output:
==================== $VAR1 = { 'a' => [ { 'c' => {} } ]\, 'b' => 1\, 'd' => {} }; $VAR1->{'a'}[0]{'c'} = $VAR1; $VAR1->{'d'} = $VAR1->{'a'}[0];
$VAR1 = { 'c' => { 'a' => [ {} ]\, 'b' => 1\, 'd' => {} } }; $VAR1->{'c'}{'a'}[0] = $VAR1; $VAR1->{'c'}{'d'} = $VAR1;
Note that the first outputs $h\, while the second outputs $m. This is because\, as the 'eval' function description states:
"In both forms\, the value returned is the value of the last expression evaluated inside the mini-program; a return statement may be also used\, just as with subroutines. The expression providing the return value is evaluated in void\, scalar\, or list context\, depending on the context of the eval itself."
The correct output could be obtained by adding a '$VAR1' at the end of the structure\, whenever the structure is self-referential.
This issue also appears to be present as late as perl 5.12.4.
Migrated from rt.perl.org#104906 (status was 'open')
Searchable as RT104906$