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A quasi-polynomial-time algorithm is presented for sampling almost uniformly at random from the n-slice of the language L(G) generated by an arbitrary context-free grammar G. (The n-slice of a language L over an alphabet is the subset L\ n of words of length exactly n.) The time complexity of the algorithm is " ?2 (n jGj) O(log n) , where the parameter "(More)
3 A preliminary version of this paper appeared as [AG91a]. 1 SUMMARY As part of a study of almost-everywhere complex sets, we investigate sets that are immune to AC 0 ; that is, sets with no innite subset in AC 0. We show that such sets exist in P PP and in DSPACE(log n log 3 n). Our main result is an oracle construction indicating that any improvement in(More)
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