problem with declaration grammar?

[Jerry Quinn]

Ellery Newcomer Wrote:

> jerry quinn wrote:
> > Ellery Newcomer Wrote:
> >>> Maybe I'm missing something.  The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules:
> >>>
> >>> BasicType2:
> >>>         *
> >>>         [ ]
> >>>         [ Expression ]
> >>>         [ Expression .. Expression ]
> >>>         [ Type ]
> >>>         delegate Parameters FunctionAttributesopt
> >>>         function Parameters FunctionAttributesopt
> >>>
> >>> Declarator:
> >>>         BasicType2 Declarator DeclaratorSuffixesopt
> >>>         BasicType2 Identifier DeclaratorSuffixesopt
> >>>
> >>> With this definition, I don't see how you can get Declarator->Identifier.
> >>>
> >>> Jerry
> >>>
> >> You are correct. BasicType2 can match nothing. It should also be able to 
> >> match what it does above multiple times.
> > 
> > As I'm looking at this further, there seems to be more issues.  In particular, I don't think the grammar can parse:
> > 
> > int (*x)(char);
> > 
> > as specified.  Doing so gives (my best attempt)
> > 
> > Decl -> BasicType Declarators ;
> > BasicType -> int
> > Declarators -> DeclaratorInitializer
> > DeclaratorInitializer -> Declarator
> > Declarator -> BasicType2 Identifier DeclaratorSuffixes
> > BasicType2 -> NULL (assuming that the grammar should be revised like this)
> > Identifier -> BAD PARSE
> > 
> > 
> 
> yeah, if you haven't figured out by now, the grammar is a bunch of hooey.
> 
> I spent like a month building an ANTLR grammar based on the above, and 
> then realized much of it was garbage.
> 
> Then I spent two months going through the source code and rewriting most 
> of the rules. Just got done with it a week or two ago :) That was all 
> version 1, but it looks the same, so if memory serves the above rules 
> should look something like this:
> 
> BasicType2_x:
> 	*
> 	[ ]
> 	[ Expression ]
> 	[ Expression .. Expression ]
> 	[ Type ]
> 	delegate Parameters FunctionAttributesopt
> 	function Paramters FunctionAttributesopt
> BasicType2:
> 	BasicType2_x
> 	BasicType2 BasicType2_x
> 	epsilon
> Declarator:
> 	BasicType2 Identifier DeclaratorSuffixesopt
> 	BasicType2 ( Declarator ) DeclaratorSuffixesopt
> 
> Apologies for any BNF misuse

Cool.  Do you feel like posting the whole thing somewhere?  

As an aside comment, it might be better from a grammar perspective to make usage of BasicType2 optional, rather than have the epsilon in the BasicType2 rule itself.  Then every rule would consume at least 1 token, and _opt is the only expansion shortcut needed.

In the form show, you can simplify the BasicType2 rule to

BasicType2:
  BasicType2 BasicType2_x
  epsilon