Re: Another tweak of the ol' Mental Model

>>>>> "Ken" == Ken Lacrosse <[email protected]> writes:

Ken> Howdy All,  I am once again (no big surprise here) puzzled about some RecDescent
Ken> behaviour.  Would anyone care to attempt to explain in small words why the
Ken> following snippet won't parse?
Ken> --------------------------
Ken> use Parse::RecDescent;
Ken> my $parse = Parse::RecDescent->new(join '', <DATA>) or die "Bad Grammar!";

Ken> my $text = "a\nb\nc\nd\n";

Ken> my $x = $parse->lines($text);
Ken> if ($x)
Ken> {
Ken>      print "x=$x $text parsed successfully!\n";
Ken> }
Ken> else
Ken> {
Ken>      print "$text is NOT parsable!!\n";
Ken> }
Ken> __DATA__

Ken> lines: /a|b|c|d/ EOL {print "line $item[0]\n"; 1}

Ken> EOL: /\n/ {1}
Ken> --------------------------

Ken> Thanks again for taking pity on the unenlightened! :-)

Ken> Ken


I'm lost.  Your grammar will parse /^[abcd]\n/, and that's
it, but you've given it "a\nb\nc\nd\n".

Oh, I see, you're expecting it to parse the prefix.  You're
swallowing your newline (because "skip" is whitespace) between
the /a/ and the EOL, so there's no *additional* EOL to be found,
and you lose.  I was able to fix it by changing your rule
to 

   lines: <skip:''> /a|b|c|d/ EOL {print "line $item[0]\n"; 1}


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