Re: Parse::RecDescent

in reply to Parse::RecDescent

This seems like a good place to mention that you'll need to place use statements in a startup block to take advantage of any Perl 5.10-isms.

Code slightly modified from an example in Advanced Perl 2nd Edition:

use Modern::Perl;

use Parse::RecDescent;

my $grammar = q{
    { use Modern::Perl }
    GameTree  : "(" Sequence GameTree(s?) ")"
    Sequence  : Node(s)
    Node      : ":" Property(s) { say "I saw a node!" }
    Property  : PropIdent PropValue(s)
    PropIdent : /[A-Z]+/
    PropValue : { extract_bracketed($text, '[ ]') }
};
my $sgf_parser = Parse::RecDescent->new($grammar);
undef $/;
my $sgf = <DATA>;
say $sgf_parser->GameTree($sgf);

__DATA__
(:GM[1]FF[4]AP[CGoban:2]ST[2]RU[Japanese]
PW[Honinbo Shuwa]PB[Yasuda Shusaku]
WR[7d]BR[5d]
 :B[qd]:W[dc]:B[pq]:W[oc]:B[cp]:W[qo]
 :B[pe]C[This is the famous Shusaku opening".])
[download]

I could be wrong, of course. This is how I got the thing to run with say in the action, though.

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Re^2: Parse::RecDescent by ikegami (Patriarch) on Mar 19, 2009 at 17:20 UTC
No, you're right. What's in the top-level curlies ends up being top-level code in the package. My parsers always look like: `use strict; use warnings; my $grammar = <<'__EOI__'; { use strict; use warnings; } ... __EOI__` [download] Note the use of heredocs. Much better than `q{}` since you don't have to escape some backslashes and some curlies. For example, to have a production match a single backslash, Single quote heredoc: `rule: /\\/` Single quote literal: `rule: /\\\/` or `rule: /\\\\/`	[reply] [d/l] [select]

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Re^2: Parse::RecDescent
by ikegami (Patriarch) on Mar 19, 2009 at 17:20 UTC

No, you're right. What's in the top-level curlies ends up being top-level code in the package. My parsers always look like:

use strict;
use warnings;

my $grammar = <<'__EOI__';

    {
        use strict;
        use warnings;
    }

    ...

__EOI__
[download]

Note the use of heredocs. Much better than q{} since you don't have to escape some backslashes and some curlies. For example, to have a production match a single backslash,

Single quote heredoc: rule: /\\/
Single quote literal: rule: /\\\/ or rule: /\\\\/

[reply]
[d/l]
[select]

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