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Id: 69225
Status: open
Priority: 0/
Queue: Regexp-Grammars

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Owner: Nobody in particular
Requestors: lhebblethwaite [...] btinternet.com
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Subject: <error: msg> does not appear
Date: Fri, 1 Jul 2011 11:27:11 +0100 (BST)
To: "bug-Regexp-Grammars [...] rt.cpan.org" <bug-Regexp-Grammars [...] rt.cpan.org>
From: Leigh Hebblethwaite <lhebblethwaite [...] btinternet.com>
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Hi, Please excuse me if this is a daft question. I have a simple grammar as an example. The grammar includes a <error:> directive. The grammar seems to be correct in that it succeeds when it should and fails when it should. However, the error message is never output. I don't know whether this is a user error or a problem with the module. Here is the grammar:     my $parser = qr{         <dml_proc>         <rule: dml_proc>  dml <name> <dml_attr> end-dml         <rule: dml_attr>  current_of_cursor                           | has_returning                           | uses_current_user                           | <error: Invalid attribute>         <token: name>     [A-Za-z0-9_]+     }xms; Tested with the string "dml aname has_returning end-dml" the parse succeeds as it should. Tested with the string "dml aname xxxx end-dml" the parse fails as it should. I would expect to see an error message produced by the <error: > directive as 'xxxx' does not match any of the possible attributes. I don't see this error message. I am using Regexp::Grammars 1.012 on ActivePerl on Windows XP. Here is the 1st line output by 'perl -v': This is perl 5, version 12, subversion 3 (v5.12.3) built for MSWin32-x86-multi-thread I attach a short script which demonstrates the problem. Thank you for your attention. Any help is very much appreciated. Regards, Leigh.
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Subject: Re: [rt.cpan.org #69225] <error: msg> does not appear
Date: Fri, 1 Jul 2011 21:11:05 +1000
To: bug-Regexp-Grammars [...] rt.cpan.org
From: Damian Conway <damian [...] conway.org>
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Hi Leigh, The module documentation explains how to access the error messages, which appear in the special @! variable: Error messages The "<error: MSG>" directive queues a conditional error message within @! and the demonstration files demo/demo_error.pl and demo/demo_pos.pl illustrate how to print the error messages. For example, in demo/demo_pos.pl: while (my $input = prompt) { if ($input =~ $grammar) { use Data::Show; show %/; } else { say 'Failed: '; say for @!; <----- This line prints the error messages if the grammar fails } } I will look at improving the documentation to make it clearer that this is how the error message interface works. Thanks for the feedback, Damian
Subject: Re: [rt.cpan.org #69225] <error: msg> does not appear
Date: Fri, 1 Jul 2011 12:41:17 +0100 (BST)
To: "bug-Regexp-Grammars [...] rt.cpan.org" <bug-Regexp-Grammars [...] rt.cpan.org>
From: Leigh Hebblethwaite <lhebblethwaite [...] btinternet.com>
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Thanks Damian, That's a really quick response! I missed the significance of @!. Thanks for putting me right. Regards, Leigh. Show quoted text
________________________________ From: "damian@conway.org via RT" <bug-Regexp-Grammars@rt.cpan.org> To: lhebblethwaite@btinternet.com Sent: Friday, 1 July 2011, 12:11 Subject: Re: [rt.cpan.org #69225] <error: msg> does not appear <URL: https://rt.cpan.org/Ticket/Display.html?id=69225 > Hi Leigh, The module documentation explains how to access the error messages, which appear in the special @! variable:     Error messages       The "<error: MSG>" directive queues a conditional error message within @! and the demonstration files demo/demo_error.pl and demo/demo_pos.pl illustrate how to print the error messages. For example, in demo/demo_pos.pl:     while (my $input = prompt) {         if ($input =~ $grammar) {             use Data::Show;             show %/;         }         else {             say 'Failed: ';             say for @!;      <----- This line prints the error messages if the grammar fails         }     } I will look at improving the documentation to make it clearer that this is how the error message interface works. Thanks for the feedback, Damian


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