Calling nearley-test on a specific grammar results in 100% cpu usage and running for an indefinite amount of time

[naissur]

Calling nearley-test on a specific grammar results in 100% cpu usage and running for an indefinite amount of time

[kach]

This is actually expected behavior! You've found a very interesting corner-case where there are an infinite number of possible parsings of the empty string:

"" = null = .:* (null) .:* = .:* (.:* (null) .:*) .:* = …

where each .:* matches zero .'s. Nearley tries to give you all of these parsings, so it goes into an infinite loop.

Depending on what you're trying to do, there are different ways to fix this grammar so that it isn't ambiguous. Let me know if you need any help.

[naissur]

Oh, that's cool! Thank you for explaining :)

The original reason for this behavior was a typo - a -> .:* a .:* should have been b -> .:* a .:*, so it's no longer infinitely ambiguous :).

Thanks for a cool project!