On Twist-Closed Trios: A New Morphic Characterization of r.e. Sets
نویسنده
چکیده
We show that in conjunction with the usual trio operations the combination of twist and product can simulate any combination of intersection, reversal and 1 2 . It is proved that any recursively enumerable language L can be homomorphically represented by twisting a linear context-free language. Indeed, the recursively enumerable sets form the least twist-closed full trio generated by dMIR:= {wcwrev | w ∈ {a, b}∗}.
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تاریخ انتشار 1997