day38 - Consequences We cannot decide if the set of valid...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
10/4/11 Dec 2, © UCF (Charles E. 11 Consequences We cannot decide if the set of valid terminating traces of an arbitrary machine M are finite. Put differently, we cannot decide if there is an upper bound on the length of any valid trace.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
10/4/11 Dec 2, © UCF (Charles E. 22 1981, Again Theorem 5: The problem to determine, for an arbitrary context free language L, if there exist a finite n such that Ln = Ln+1 is undecidable.
Background image of page 2
10/4/11 Dec 2, © UCF (Charles E. 33 L for Machine M L1 = { C1# C2R $ | C1, C2 are configurations }, L2 = { C1#C2R$C3#C4R … $C2k- 1#C2kR$ | where k & 1 and, for some i, 1 - i < 2k, Ci -M Ci+1 is false }, L = L1 & L2 “ {& }.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
10/4/11 Dec 2, © UCF (Charles E. 44 Finite Power Property L is context free. Any product of L1 and L2, which contains L2 at least once, is L2. For instance, L1 & L2 = L2 & L1 = L2 b L2 = L2. This shows that (L1 & L2)n = L1n { L2. Thus, Ln = ±J} & L1 & L12 …
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/03/2011 for the course COT 5310 taught by Professor Staff during the Spring '08 term at University of Central Florida.

Page1 / 8

day38 - Consequences We cannot decide if the set of valid...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online