Support optional rules when parsing about bullwinkle HOT 3 OPEN

Optional rules are supported in Bullwinkle, but they have to be written following the BNF syntax, where the "?" symbol is not allowed. So instead of writing:

<S> := <A> <B>?;

you should write instead:

<S> := <A> <B> | <A>;

There are two ways to parse S: either as A followed by B, or as A alone --which has the effect of making B optional.

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I came to the same conclusion. But I felt re-writing the whole Java BNF this way would be too much work and would make for a really ugly BNF anyway. So I added the feature myself.

I'm thinking of sharing the code but will wait until Bullwinkle is released under MIT.

from bullwinkle.

I just changed the header comments to the MIT license.

from bullwinkle.