Re^2: Perl data notation

That makes it possible to eval them back to existence.

This holds for basic data structures, but fails for three cases (I know of):

Repeated entries for the same reference
Subroutine references
Objects with hidden lexical content

That first one is the most common; consider

 perl -MData::Dumper -e 'my $ref = []; print Dumper eval Dumper [$ref,
+ $ref];
[download]

which outputs

$VAR1 = [
          [],
          undef
        ];
[download]

and (thankfully) fails under strict.

</pedantic>

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

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Re^3: Perl data notation by Anonymous Monk on Jul 15, 2014 at 16:06 UTC
It may not solve all the problems you mentioned, but: `$ perl -MData::Dump=pp -le '$ref = []; print pp eval pp [$ref, $ref];' do { my $a = [[], 'fix']; $a->[1] = $a->[0]; $a; }` [download]	[reply] [d/l]
Re^3: Perl data notation by ikegami (Patriarch) on Jul 25, 2014 at 04:02 UTC
D::D can handle #1. You just gotta use Purity=1 D::D can handle #2. You just gotta use Deparse=1	[reply]
Re^3: Perl data notation by davido (Cardinal) on Jul 15, 2014 at 22:25 UTC
I believe Storable will handle subrefs, but the eval problem doesn't go away. Storable does provide a way for the user to get between the input and the eval though. And of course Storable's frozen output is anything but legible. Dave	[reply]
Re^4: Perl data notation by kennethk (Abbot) on Jul 16, 2014 at 00:18 UTC
For the truly motivated, B::Deparse can serialize into a legible format. `use strict; use B::Deparse; my $deparse = B::Deparse->new(); my $func = sub { my %hash = @_; return $hash{a}; }; my $body = $deparse->coderef2text($func); print $body;` [download] You could condition the tree by crawling it and clobbering anything with reftype `CODE` with `sprintf 'sub %s', $deparse->coderef2text($hash{key})`. But this still kills closures, and plus is a terrible, terrible idea. #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re^3: Perl data notation by Anonymous Monk on Jul 19, 2014 at 09:09 UTC
Again, it doesn't solve all the problems you mentioned, but: `$ perl -MData::Dumper -le '$Data::Dumper::Deparse=1; \ print Dumper eval Dumper sub { $x++; print "Hello"; }' $VAR1 = sub { ++$x; print 'Hello'; };` [download]	[reply] [d/l]