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I agree. These definitions make it clearer that each is a superset of the next. That's nice. I'll go ahead and change the table to use those definitions. The "maybe S->ε" part can go in a sentence after the table, since it also needs to explain that if you use that form, you can't have S on the right side for Type-1. I changed it from a hierarchy of languages to a hierarchy of grammars, and got rid of the "Chomsky-n" and "CHn" names before, but it slipped back in when the bullets were re-expanded. I'll make that change again. -LC Useful links for further work * [1] * [2] |
I'm curious about the names "Chomsky-n" and "(CHn)". I've always heard people talk of "Type-n" grammars and languages, but not "Chomsky-n" languages. None of my books have it either. A web search turns up lots of hits on "Type-0 grammar" but none on "Chomsky-0". The same is true for the papers archived at [1]. Is this term in widespread use? Or did a textbook coin it for internal use? -LC
As far as the "Chomsky-n" names are concerned, I didn't introduce those and I also haven't seen them anywhere before. The hierarchy is usually presented as a hierarchy of grammars and not of languages, so I feel we should do the same. -- JanHidders
I changed it from a hierarchy of languages to a hierarchy of grammars, and got rid of the "Chomsky-n" and "CHn" names before, but it slipped back in when the bullets were re-expanded. I'll make that change again. -LC