Parse grammar via RecDescent parser

the_dark_lord has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Parse grammar via RecDescent parser by Anonymous Monk on May 17, 2016 at 11:56 UTC
Youve heard of arrays? Use an array, or a hash	[reply]
Re: Parse grammar via RecDescent parser by the_dark_lord (Novice) on May 17, 2016 at 13:18 UTC
Hi I would use arrays or a hash if I could. I would have to specify that array in the grammar which would mean that it would be inside the parser's namespace and cannot be accessed from outside. I am looking for some way I could store the data in the parser itself and then retrieve later after all statements in the file have been tokenized.	[reply]
Re^2: Parse grammar via RecDescent parser by Corion (Patriarch) on May 17, 2016 at 13:43 UTC
You know that you can get the parse tree from Parse::RecDescent with the `<autotree>` directive? This should give you all the data that is available in the structure and content of your source file. Maybe you can show us a short, workable example of maybe 20-35 lines that shows what you have and where you are trying to get to?	[reply] [d/l]
Re^2: Parse grammar via RecDescent parser by GotToBTru (Prior) on May 17, 2016 at 16:30 UTC
Why would you need to specify the array in the grammar? Your plan is to store the data in the parser. But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us. Romans 5:8 (NASB)	[reply]
Re^2: Parse grammar via RecDescent parser by the_dark_lord (Novice) on May 17, 2016 at 14:17 UTC
Hi My grammar rule looks like the following: `file_exists: 'file(' filename ')' { $return = "-e $item{ 'filename' } }` [download] Now I would want this rule to do two things: 1) return the string "-e < filename>" so that I can eval it later and check existence of that file 2) store the file names which I can retrieve later I can achieve only one of the two from the grammar that I have. I want to do both.	[reply] [d/l]
Re^3: Parse grammar via RecDescent parser by Corion (Patriarch) on May 17, 2016 at 14:28 UTC
Why not store both, the string and the filename? `file_exists: 'file(' filename ')' { $return = [ "-e $item{ 'filename' }", $item{ 'filename' +}] }` [download]	[reply] [d/l]
Re^4: Parse grammar via RecDescent parser by the_dark_lord (Novice) on May 17, 2016 at 14:33 UTC
Re^5: Parse grammar via RecDescent parser by Corion (Patriarch) on May 17, 2016 at 14:39 UTC
Re^3: Parse grammar via RecDescent parser by Anonymous Monk on May 17, 2016 at 15:02 UTC
guessing... `file_exists: 'file(' filename ')' { $return = "-e $item{ 'filename' }; push @somepackagename +::savedfilenames, $item{ 'filename' } }` [download] Then outside the parser, retrieve the array as @somepackagename::savedfilenames	[reply] [d/l]
Re^4: Parse grammar via RecDescent parser by the_dark_lord (Novice) on May 17, 2016 at 15:12 UTC
Re^5: Parse grammar via RecDescent parser by Corion (Patriarch) on May 17, 2016 at 15:24 UTC
Some notes below your chosen depth have not been shown here
Re: Parse grammar via RecDescent parser by polettix (Vicar) on May 19, 2016 at 13:21 UTC
You might use `$thisparser->{local}` to collect stuff along the way (as opposed to using package variables): `#!/usr/bin/env perl use strict; use warnings; use Parse::RecDescent; use Data::Dumper; my $grammar = <<'END'; foo: word(s) word: /\S+/ { push @{$thisparser->{local}}, lc $item[1]; $return = uc $item[1]; } END my $parser = Parse::RecDescent->new($grammar); my $what = $parser->foo("Foo bAr baZ"); print Dumper $what, $parser->{local}; __END__ $VAR1 = [ 'FOO', 'BAR', 'BAZ' ]; $VAR2 = [ 'foo', 'bar', 'baz' ];` [download] The docs say that ... the use of `$this...->{local}` is always safe. You will have to reset this field if you plan to call the same parser multiple times and you don't want each run to add its items to those of the previous runs. And, of course, nothing prevents you from using `local` for storing more complicated data structures. This said, I suggest that you read Corion's advices again. It seems like you're trying to mix parsing and evaluation, which might not be the wisest thing to do. perl -ple'$_=reverse' <<<ti.xittelop@oivalf Io ho capito... ma tu che hai detto?	[reply] [d/l] [select]