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6/13/01 6:05:25 PM, Marcus Carr <mrc@a...> wrote: >Jason Chalecki wrote: > >> ((a, b)*, a) essentially represents the language where the first and >> last letter is a. Additionally, if there are b's, a and b must >> alternate. So (a, (b, a)*) matches the same language and is >> deterministic, correct? > >Yes, but the original model was allowed to finish with either a or b - the >final a had a question mark. To model that with your approach would result >in (a, (b, a?)*), which allows a string of b's with no intervening a's. >Either way, you've changed the model. Applying the subset construction to the NFA associated with the original model ((a, b)*, a?), I end up with a two-state DFA in which both states are final: A B 0 1 - 1 - 0 but I can't figure out how to express it as a content model (or regular expression).
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