Regular expressions

[Thomas Weigert]

Dear all,

I am struggling with which parts of Perl's regular expression syntax is supported in lexeme rules and which are not. For example, I was trying to write a simple rule with zero-width look ahead, but marpa does not like it:

PICSINGLEDOT ~ [.](?=\.)

The manual seems to imply that whatever is in Perl is ok, but that seems far from true.

Does anybody have any guidance to offer here?

Thanks, Th.

[Jeffrey Kegler]

Marpa::R2's SLIF only supports the character class part of Perl's RE's:  https://metacpan.org/pod/distribution/Marpa-R2/pod/Scanless/DSL.pod#Character-classes

The SLIF has its own mechanisms for doing the equivalent of lookahead.  One in particular is pre-lexeme events: https://metacpan.org/pod/distribution/Marpa-R2/pod/Event.pod#Pre-lexeme-events

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[Ron Savage]

Also, on Marpa's home page (http://savage.net.au/Marpa.html#Perl_Packages) you'll find various modules which use that pre-lexeme event mechanism. These are just mine; there may be others:

o GraphViz2::Marpa

o MarpaX::Demo::StringParser (used to investigate issues before incorporation into the above)

o MarpaX::Languages::Perl::PackUnpack

o Text::Balanced::Marpa

o Text::Delimited::Marpa

The World is Your Now-parsable Oyster!