decorate AST with input line numbers?

[stefan]

Hi, folks. 

I'm a MARPA newbie, so my apologies if I am asking a question which is too obvious.

I have a prototype parser for a DSL - my customer needs me to deliver an AST for it, where each node knows the line number (and perhaps even column number) at which that expression or construct began in the input stream.

I have pored over the copious MARPA documentation and commentary by users, but I haven't yet understood how I can do this.

I thought perhaps I could attach an event to every terminal, and have the event callback ask the parser where it is in the input stream? If so, I'm not even sure how to do that.

I would be grateful for any advice.

-stefan

 

[Jeffrey Kegler]

I'm actually rusty at this, but I think the most direct way is to use the "start" and "length" item descriptors in an array descriptor to get input stream start location and length in characters: http://search.cpan.org/~jkegl/Marpa-R2/pod/Semantics.pod#Array_descriptor_actions

To convert input stream locations to line/column locations, you can use the $recce->line_column() method: http://search.cpan.org/~jkegl/Marpa-R2/pod/Scanless/R.pod#line_column()

I hope this helps! -- jeffrey

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[Ron Savage]

Hi Stefan

http://savage.net.au/Perl-modules/html/marpa.faq/faq.html#q119