We describe a new elementary reduction of two-way automata to one-way automata. The reduction is based on the subset construction rather than on crossing sequence analysis.

As a result of the work of Turing, Post, Kleene and Church [1, 2, 3, 9, 10, l l 12, 17, 18] it is now widely accepted ~ that the concept of "computable" as applied to a function ~ of natural numbersâ€¦ (More)

The classic results of logic programming are based on an underlying equality relation of syntactic identity. Jaffar, Lassez and Maher [2] have shown how to extend these results, for definite clauseâ€¦ (More)

Cobham has observed that Raphael Robinson's well known essentially undecidable theory R remains essentially undecidable if the fifth axiom scheme (x < ~ v fi < x) is omitted. We note that whether theâ€¦ (More)