Left-recursion improvements.

[veelo]

This brings the parsing of a sample Extended Pascal file down from 13 minutes to 17 seconds. The mistake was not to assign the result of std.algorithm.mutation.remove, which caused an array to grow to a massive size and memoization to never be reenabled. (This is now on row 562.)

It also removes quite a bit of complexity and some requirements that I never really understood why were necessary. Now it appears they aren't.

This is worth a patch-level version bump, I think.

[PhilippeSigaud]

OK, done. I merged it and created a new patch release (v0.4.2). I suppose the speed improvements will also be visible for other grammars than EP?

…

On Sat, Apr 15, 2017 at 2:52 AM, Bastiaan Veelo ***@***.***> wrote: This brings the parsing of a sample Extended Pascal file down from 13 minutes to 17 seconds. The mistake was not to assign the result of std.algorithm.mutation.remove, which caused an array to grow to a massive size and memoization to never be reenabled. (This is now on row 562.) It also removes quite a bit of complexity and some requirements that I never really understood why were necessary. Now it appears they aren't. This is worth a patch-level version bump, I think. ------------------------------ You can view, comment on, or merge this pull request online at: #226 Commit Summary - Fix blocking of memoization. The error was in the use of std.algorithm.mutation.remove, which confusingly does not mutate the range, but returns a new range — which was never used. - Replace “keys.canFind” with “in”. - Comments about stopper rules and blocked memoization. - Use the same memo-blocking array for all left-recursive rules. - Prevent duplicates. File Changes - *M* pegged/grammar.d <https://github.com/PhilippeSigaud/Pegged/pull/226/files#diff-0> (239) Patch Links: - https://github.com/PhilippeSigaud/Pegged/pull/226.patch - https://github.com/PhilippeSigaud/Pegged/pull/226.diff — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#226>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAjYpz1WwqovYUmbWKLxEp9aubqyXdGvks5rwBTCgaJpZM4M-NFj> .

[veelo]

Thanks.

I suppose the speed improvements will also be visible for other grammars than EP?

If the grammar is left-recursive then yes.

Although much better, 17 seconds is still really slow. This is a file that is compiled by the Prospero compiler in just 99 milliseconds... I am thinking that top-down parsing is not efficient for this language, but I'll see if I can do a bit more profiling.