I want to chime in and mention that Rats! has had a runtime interface for
pruning memorization tables for quite a while. The C parser uses this interface
to throw away the table after each external declaration. For real-world C code
that makes all the difference between running out of memory and keeping it
manageable. But I would agree that moving that operation into the grammar and
ensuring its correctness automatically certainly is a good thing.
Robert
On Mar 29, 2013, at 3:36 PM, Juancarlo Añez <apal...@gmail.com> wrote:
> After, the recent experiments, I reviewed the implementation of cut in Grako.
>
> Grako's implementation of cut is in the spirit of Prolog, which means that a
> cut applies only to the nearest choice (optional, closure) in the runtime
> stack. That means that memos for positions before that of the last choice
> have a non-zero theoretical probability of being reused.
>
> The explanation for the low impact of my optimistic memo pruning on
> performance should be that the grammar is for a structured, largely
> unambiguous, and quite probably LL(k) programming language, which makes it
> unlikely that previous memos are reused after any structured construct ("IF"
> cut) has been entered.
>
> Cheers,
>
> --
> Juancarlo Añez
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