The tricky part is to make it work for arbitrary values, i.e. drop the assumption the symbols for Empty_Marker and '-' are not going to be used in any node's value.
Here's such a solution in Perl, tests included:
#!/usr/bin/perl use warnings; use strict; package Node { use Moo; has value => (is => 'ro', required => 1); has left => (is => 'ro', isa => sub { shift->isa('Node') or die }); has right => (is => 'ro', isa => sub { shift->isa('Node') or die }); my $_escape_value = sub { my ($self) = @_; my $value = $self->value; $value =~ s/$_->[0]/\\$_->[1]/g for [qr/\\/ => '\\'], [qr/"/ => '\''], [qr/\(/ => '['], [qr/\)/ => ']']; return $value }; my $unescape = sub { my ($value) = @_; $value =~ s/(?<!\\)\\$_->[0]/$_->[1]/g for [qr/\]/ => ')'], [qr/\[/ => '('], [qr/'/ => '"']; $value =~ s/\\\\/\\/g; return $value }; my $parse = sub { my ($rest) = @_; my $pos = '(' eq substr $rest, 0, 1; my $rank = $pos; until (0 == $rank) { ++$rank if '(' eq substr $rest, $pos, 1; --$rank if ')' eq substr $rest, $pos, 1; ++$pos; } my $left = substr $rest, 0, $pos; my $right = substr $rest, $pos + ($pos != length $rest); length $_ and $_ = __PACKAGE__->deserialize($_) for $left, $right; return $left, $right }; sub serialize { my ($self) = @_; my $value = $self->$_escape_value; my ($left, $right) = map $_ ? $_->serialize : "", $self->left, $self->right; return '(' . join(',', qq("$value"), $left, $right) . ')' } sub deserialize { my ($class, $string) = @_; return undef unless length $string; my ($value, $rest) = $string =~ /^\("([^"]*)",(.*)\)$/sg; $value = $unescape->($value); my ($left, $right) = $parse->($rest); return $class->new(value => $value, (left => $left) x !! ref $left, (right => $right) x !! ref $right) } }; use Test::More tests => 7; my $node1 = 'Node'->new( value => 'root', left => 'Node'->new( value => 'left', left => 'Node'->new(value => my $left_left = 'left.left')), right => 'Node'->new(value => 'right'), ); is 'Node'->deserialize($node1->serialize)->left->left->value, $left_left; my $node2 = 'Node'->new( value => my $empty = "", right => 'Node'->new(value => my $special_chars = '("[,\'\\]"))', right => 'Node'->new( value => my $newline = "1\n2"))); is 'Node'->deserialize($node2->serialize)->value, $empty; is 'Node'->deserialize($node2->serialize)->right->value, $special_chars; is 'Node'->deserialize($node2->serialize)->right->right->value, $newline; my $node3 = 'Node'->new(value => $node1->serialize, left => 'Node'->new(value => $node2->serialize)); is 'Node'->deserialize($node3->serialize)->value, $node1->serialize; is 'Node'->deserialize($node3->serialize)->left->value, $node2->serialize; my $super = $node3->serialize; $super = 'Node'->new( value => 'Node'->deserialize($super)->serialize )->serialize for 1 .. 6; my $root = $super; $root = 'Node'->deserialize($root)->value for 1 .. 8; is $root, 'root';
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The tricky part is to make it work for arbitrary values, i.e. drop the assumption the symbols for Empty_Marker and '-' are not going to be used in any node's value.
Here's such a solution in Perl, tests included: