Perl 6 - the future is here, just unevenly distributed

IRC log for #marpa, 2016-05-11

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All times shown according to UTC.

Time Nick Message
01:48 ilbot3 joined #marpa
01:48 Topic for #marpa is now Start here: http://savage.net.au/Marpa.html - Pastebin: http://scsys.co.uk:8002/marpa - Jeffrey's Marpa site: http://jeffreykegler.github.io/Marpa-web-site/ - IRC log: http://irclog.perlgeek.de/marpa/today
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04:16 ronsavage Fair enough. I looked at it like ! $X being negation of $X.
04:41 rns idiosyncrat, ronsavage: when the bang ("!") symbol means visible, then A ::= B C D E will set all RHS symbols as visible, but in A ::= B C! D! E onle C and D will be visible.
04:42 rns So, will using the bang even once, as in A ::= B C! D E will render B D, and E invisible, will it not?
05:04 idiosyncrat_ rns: Yes
05:07 idiosyncrat_ Only <C> would be visible.
05:07 idiosyncrat_ Good night!
05:13 rns idiosyncrat: looks good
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06:18 ronsavage In my grammars, 99.99% of tokens would be visible, so I think attaching a special symbol to token which should be invisible makes /much/ more sense than having a grammar riddled with !s or whatever.
06:19 ronsavage And as an alternative to !, how about ^ to mean invisible, somewhat akin to the ^ in [^A]?
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15:36 idiosyncrat_ "Data::Dumper version 2.125 required--this is only version 2.124 at /home/cpan/pit/bare/conf/perl-5.10.1/.cp​anplus/5.10.1/build/986Be2ZrPl/Marpa-R3-​4.001_006/blib/lib/Marpa/R3/Version.pm line 10"
15:36 idiosyncrat_ from http://www.cpantesters.org/cpan/report​/85b3192e-16e5-11e6-829f-59a5aef69d38 and a few other tests
15:43 idiosyncrat_ I think this is a testbed problem -- I'm requiring Data::Dumper 2.125
15:46 idiosyncrat_ ronsavage: re http://irclog.perlgeek.de/m​arpa/2016-05-11#i_12462475
15:46 idiosyncrat_ I'd be thinking of using the minus sign ("-"), so that
15:46 idiosyncrat_ A ::= B C D- E
15:47 idiosyncrat_ meant that only <B>, <C> and <E> were visible.
15:48 idiosyncrat_ The caret ("^") is used in RE's as a beginning anchor, and I think would probably suggest some such meaning to SLIF users.
17:24 idiosyncrat_ re http://irclog.perlgeek.de/m​arpa/2016-05-11#i_12464969
17:25 idiosyncrat_ Note that you would not be allowed to mix minuses and bangs in the same RHS alternative.  That is,
17:25 idiosyncrat_ A ::= B C! D- E
17:25 idiosyncrat_ would be a fatal error.
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22:51 ronsavage Re: http://irclog.perlgeek.de/m​arpa/2016-05-11#i_12462311. This is what worries me. Sometimes absence of ! means symbols are visible, and sometimes its absence means they are invisible? Sorry, but that's irrational.
23:40 idiosyncrat_ Well, I could omit the "-" syntax -- because I'm thinking the "!" for its opposite is more natural ...
23:41 idiosyncrat_ that does mean, though, that if you have the rule "A :: B C D E F"
23:41 idiosyncrat_ you have to write it as
23:42 idiosyncrat_ (assumming you want to omit just <D>)
23:42 idiosyncrat_ A ::= B! C! D E! F!
23:42 idiosyncrat_ or
23:42 idiosyncrat_ A ::= (! B C !) D (! E F !)

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