Pegged, a Parsing Expression Grammar (PEG) generator in D

[Andrei Alexandrescu]

On 3/10/12 5:56 PM, Andrej Mitrovic wrote:
> I see you are not the only one who started writing string array
> literals like this:
>
> enum PEGCode = grammarCode!(
>       "Grammar<- S Definition+ EOI"
>      ,"Definition<- RuleName Arrow Expression"
>      ,"RuleName<- Identifier>(ParamList?)"
>      ,"Expression<- Sequence (OR Sequence)*"
> );
>
> IOW comma on the left side. I know it's not a style preference but
> actually a (unfortunate but needed) technique for avoiding bugs. :)
>
> So can you use this to actually parse D code, extract syntax trees and
> stuff like that? I'm clueless about parsing but it looks very neat.
> Nice work!

I, too, think this is very significant work! Suggestion for Philippe: 
instead of this:

enum PEGCode = grammarCode!(
      "Grammar <- S Definition+ EOI"
     ,"Definition <- RuleName Arrow Expression"
     ,"RuleName   <- Identifier>(ParamList?)"
     ,"Expression <- Sequence (OR Sequence)*"
);

how about this:

enum PEGCode = grammarCode!("
     Grammar <- S Definition+ EOI;
     Definition <- RuleName Arrow Expression;
     RuleName   <- Identifier>(ParamList?);
     Expression <- Sequence (OR Sequence)*;
");

Splitting on ";" is trivial and makes client code considerably easier to 
play with.

I'll get back to this.


Andrei