Sent from my iPhone
On May 27, 2009, at 12:55 PM, Gavin Lambert <[email protected]>
wrote:
> At 04:55 28/05/2009, Jim Idle wrote:
>> The idea is that a token is defined as specific type, but can also
>> exist as another type at the same time. So, if the parser needs to
>> know if there is an ID, the code generated asks if the token is a
>> real ID OR has a superimposed ID and so reduces all the complexity
>> of using keywords as identifiers (and probably other case, but this
>> is the specific problem domain), to an extra || operation and an
>> additional LA type operation, something like this:
>>
>> int LA1_0 = input.LA(1);
>> int LA1_0_s = input.LAS(1);
>>
>> if ( (LA1_0==ID)||(LA1_0_s==ID ) {
>> alt1=1;
>> }
>
> Shouldn't any number of other token types be able to be superimposed
> on a token? It seems like a waste to arbitrarily restrict this to
> one other type.
>
Perhaps but I have not through all the implications of that. I think
performance might suck and I can see people getting into all sorts of
trouble.
> (In terms of implementation, you could make LAS return a BitSet of
> the possible types, or you could leave the decision-making to the
> token itself; eg. use TokenType instead of int and have it define
> comparison and containment operations. Or something else along
> those lines.)
>
I thought about bollean LAS(1, Toktype) but again it means more
complicated code and then there is the DFA to consider etc
Anyway I will have a play with it soon and see if it is even practical.
Jim
List: http://www.antlr.org/mailman/listinfo/antlr-interest
Unsubscribe:
http://www.antlr.org/mailman/options/antlr-interest/your-email-address
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"il-antlr-interest" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/il-antlr-interest?hl=en
-~----------~----~----~----~------~----~------~--~---
