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.
(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.)
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