# Recognizable

### A non-Turing-recognizable language

CS 360: Introduction to the Theory of Computing John Watrous, University of Waterloo A non-Turing-recognizable language 1 O VERVIEW Thus far in the course we have seen many examples of decidable languages—they include all of the regular and context-free languages, as well as many other ...

### Practice Problems for Final Exam CS 341: Foundations of ...

Turing-recognizable language x. co-Turing-recognizable language xi. Countable and uncountable sets xii. Language Ais mapping reducible to language B, A m B xiii.

### Examples of undecidable languages

CS 360: Introduction to the Theory of Computing John Watrous, University of Waterloo (typesetbyGus Gutoski) Examples of undecidable languages In a previous handout we saw that the language L d ={w∈* ∗: w6∈L (M w) } is non-Turing-recognizable.

### Recitation7: Reducibility, Rice'sTheorem

Classify each of the follo wing problems as either (D) decidable, (R) recognizable but not decidable, (C) co-recognizable but not decidable, or (N) ...

### f is a "unary function symbol":

From "Complexity of Computation" (ed. R. Karp) SIAM-AMS Proceedingn Volume 7 1974 Generalized First-Order Spectra and Polynomial-Time Recognizable Sets' Ronald Fagin 1.

### Variants of Turing Machines

A language is Turing-recognizable iff some nondeterministic TMrecogniz es it Proof: if: If a language is Turing-recognizable it is recognized bya DTM.

### Brand Dubai: The Instant City; or the Instantly Recognizable City

Brand Dubai: The Instant City; or the Instantly Recognizable City SAMER BAGAEEN St. Mary’s, University of Aberdeen, UK ABSTRACT With ambitions to become a hub of global commerce, a top tourist destination and a

### Problem Set4

Show that any two disjoint co-Turing-recognizable languages are separable by some decidable language. 3. (Sipser4.21) Let A be a Turing-recognizable language consisting of de-scriptionsofTuring machines, ...