Wow....Thank you thank you very much, Chas. Owens, that's great...appreciate
that :-)
William
----- Original Message ----
> From: Chas. Owens <chas.ow...@gmail.com>
> To: William <esia...@yahoo.com>
> Cc: beginner perl mailling list <beginners@perl.org>
> Sent: Friday, June 5, 2009 22:01:41
> Subject: Re: parsing data structure
>
> On Fri, Jun 5, 2009 at 09:19, William wrote:
> >
> > I have been trying for hours, to make this data structure into hash, I need
> help. Thanks.
> >
> > $str =
> > "
> > (dr1
> > foo
> > <1>(dr2 bar)
> > <2>a
> > )
> > ";
> >
> > $hash = {
> > "dr1" => {
> > "<1>" => {"dr2" => {"predicate"=> "bar"}},
> > "<2>" => "a"
> > }
> > };
> snip
> > What could be the regular expression and algorithm to make the resulting
> > hash
> ?
> snip
>
> This isn't really a job for a regex. Note that you have a recursive
> structure (parentheses can contain parentheses). When you have a
> recursive structure you are moving out of the realm of regexes and
> into the realm of parsers. A good general purpose parser is
> Parse::RecDescent[1], and you should learn to use it, but your example
> is simple enough that we don't need it. We can tokenize the stream
> fairly easily by splitting on '(', ')', '<', '>', and whitespace, then
> throwing out the whitespace characters[2]. Once we have the tokens we
> deal with each () group recursively:
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> my $s = "
> (dr1
> foo
> <1>(dr2 bar)
> <2>a
> )
> ";
>
> my @tokens = grep { /\S/ } split /([()<>\s])/, $s;
>
> my $hash = recurse(\...@tokens);
>
> use Data::Dumper;
> print Dumper $hash;
>
> sub recurse {
> my $tokens = shift;
> my $paren = shift @$tokens;
> my $key = shift @$tokens;
> die "invalid structure" unless $paren eq '(';
>
> my %hash;
> while (@$tokens) {
> my $start = shift @$tokens;
> my $subkey = shift @$tokens;
> my $end = shift @$tokens;
> die "invalid structure" unless $start eq '<' and $end eq '>';
>
> if ($tokens->[0] eq '(') {
> $hash{$key}{$subkey} = recurse($tokens);
> } else {
> $hash{$key}{$subkey} = shift @$tokens;
> }
>
> if ($tokens->[0] eq ')') {
> shift @$tokens;
> return \%hash;
> }
> }
>
> die "invalid structure";
> }
>
> 1. http://search.cpan.org/dist/Parse-RecDescent/lib/Parse/RecDescent.pm
> 2. if whitespace is allowed between '<' and '>', this will need to
> change slightly
>
> --
> Chas. Owens
> wonkden.net
> The most important skill a programmer can have is the ability to read.
>
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