A recurring error in my grammars, that I cannot fix

[Jean-Christophe Le Lann]

Hello everybody !

I'd like your advice concerning a recurring problem concerning my usage of Treetop,that I cannot fix...from time to time. I'm probably missing something.

I suspect many of you have the right idiom or habits to solve that.

I generally use Treetop like the following :

1) I define my grammar

2) I modify it to emit custom parse tree objets (that inherit  Treetop::Runtime::SyntaxNode). These classes are defined in a "parsetree.rb" file.

3) these custom objects have a to_ast method to turn them recursively into "pure" Treetop-independent classes (that constitute my final AST). I have two separate modules (ParseTree & AST) for that.

However, I hit a classical error message, that I cannot generally fix :

parsetree.rb:380:in `to_ast': undefined method `to_ast' for SyntaxNode offset=149, "":Treetop::Runtime::SyntaxNode (NoMethodError)

In this example, on this line 380 I have the following code ( it is about a finite state machine)

# in parsetree.rb

class Next < Tree
      def to_ast
        ret=Ldl::Ast::Next.new
        ret.name=ns.to_ast
        if cond
          ret.condition=cond.c.to_ast
        end
        ret.actions=acts.to_ast # <==== line 380
        ret
      end
    end

 class NextActions < Tree
      def to_ast
        eqs.elements.collect{|eq| eq.to_ast}
      end
    end

And my piece of grammar concerned by the error is :
rule nextstate
    space? 'next' space ns:identifier space? cond:('?' space? c:expression)? space
    acts:next_actions? <Ldl::ParseTree::Next>
  end 

  rule next_actions
    space? eqs:equation+ space 'end' space <Ldl::ParseTree::NextActions>
  end

I am puzzled here because it seems to me that Treetop emits a sort of "space" in place of one of my custom node...

Any idea ?

Thanks for your time

JCLL

[Jean-Christophe Le Lann]

FYI

Clifford has kindly answered my question on stackoverflow HERE

Thanks again

JCLL