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About default options ':ratchet' and ':sigspace' on rules
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Date: Fri, 2 Jun 2006 14:17:25 +0800
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Subject: About default options ':ratchet' and ':sigspace' on rules
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Approved: n...@nntp.perl.org
From: s...@csie.org (Shu-chun Weng)
Hello,
(used to post on google group but found it does not deliver)
I'm implementing "MiniPerl6" in pugs which is the first step of
writing perl 6 parser in perl 6. In module Pugs::Grammar::MiniPerl6,
http://svn.openfoundry.org/pugs/misc/pX/Common/Pugs-Grammar-MiniPerl6,
I use another perl 6 grammar to describe it. It works well several
days before when the parsing engine written in perl 5 did not
implemented :ratchet and :sigspace flags.
The grammar file can be found here:
http//svn.openfoundry.org/pugs/misc/pX/Common/Pugs-Grammar-MiniPerl6/lib/Pugs/Grammar/MiniPerl6.grammar
The "token" part is fine, but the "rule" part is extremely ugly. I can
not add additional spaces to format it.
I'd like to suggest two changes to make it easier to write rules:
1. Spaces at beginning and end of rule blocks should be ignored
since space before and after current rule are most likely be
defined in rules using current one.
1a. I'm not sure if it's "clear" to define as this, but the spaces
around the rule-level alternative could also be ignored. For
instance, look at the rule FunctionAppExpr defined in
MiniPerl6 grammar file.
rule FunctionAppExpr
{<Variable>|<Constants>|<ArrayRef>|<FunctionName>[<?ws>?<'('><?ws>?<Parameters><')'>]?}
I could not even put a new line in it. In the file, since there
are production rules, I put the brases on strange positions
to format it better.
2. I am not sure the default rule of <ws>, I couldn't found it in
S05. Currently the engine use :P5/\s+/ but I would like it to
be :P/\s*/ when it's before or after non-words and remains
the same (\s+) otherwise.
I do not subscribe this group but subscribe daily digest, so it's OK to
reply on the list. Suggestions welcome!
Cheers,
Shu-Chun Weng
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