[ragel-users] Problem with an indetermination

[Adrian Thurston]

The problem here is an ambiguity. When a space is seen it is unknown 
whether or not the space extends the name or is the beginning of the end 
("<"). You can change it to this:

name = ( token ( SP token )* )   > { _tag = p }
    %{ @value = data[_tag..p-1].pack("c*") };

full = name SP* %{ puts "--name=#{@value}--" } "<" [a-z]+ ">";

main := full;

Now on each space the value is only stored. Basically you need to mark 
the end separately from doing something about it because ever time you 
think you see the end, it may not be the end.

An alternative would be to include the SP* in name and strip trailing 
whitespace after.

-Adrian


Iñaki Baz Castillo wrote:
> Hi, I'm finishing a complete SIP protocol parser with Ragel, but I have an 
> issue I can't solve. The problem is basically the following (I use Ruby):
> 
> --------------
> name = ( token ( SP token )* )   > { _tag = p }
>   %{ @value = data[_tag..p-1].pack("c*"); puts "--name=#{@value}--"} ;
> 
> full = name SP* "<" [a-z]+ ">" ;
> 
> main := full
> --------------
> 
> I parse the following valid string:
>   'Alice Kiske <alice>'
> and I get two results for "name" node:
> 
>   --name=Alice--
>   --name=Alice Kiske--
> 
> Obviously I just want the second result, the first one shouldn't occur.
> 
> I've solved similar problems using priorities but they don't help me in this 
> issue. Any help please?
> 
> Thanks a lot.
> 
>