[antlr-interest] setting k Value Versus Predicates
gokul007 at gmail.com
Sun Feb 14 01:59:23 PST 2010
Actually i intended to ask a question, whether there are any cases under
which i should prefer predicates than increasing the value of k. Is it a
very obvious one???
On Thu, Feb 11, 2010 at 4:37 AM, Gokulakannan Somasundaram <
gokul007 at gmail.com> wrote:
> I observed the code generated for antlr parser and understood this.
> a) If i have set k = n, ANTLR keeps trying to resolve the grammar by
> reading further tokens(max n tokens), if there is an ambiguity
> b) Once it has read n tokens, then it tries the syntactic or(and) semantic
> predicates and chooses the first alternative that satisfies the predicate.
> This is implemented with if- condition, whereas the resolving of n-tokens,
> happen through switch-case.
> Now if i have a grammar(say with k=2) and the only way i can convert it
> into k=1 is by using predicates, i think i am better off staying with a
> higher value of k. In any case converting my grammar would produce x
> ambiguity warnings in y rules. We can be sure that (x >= y). So even in the
> best case of x=y ( i.e. each rule produces one ambiguity while converting to
> lower k and each one can be resolved by one if-condition), i am just
> replacing switch..case by if..condition.
> So i feel it is better off to stay with a higher value of k, than to
> resolve by predicates. Can i safely make this assumption?
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