If L and L' are recursively enumerable, then L is

Related MCQs

• The grammar whose productions are <stmt> → if id then <stmt> <stmt> → if id then <stmt> else <stmt> <stmt> → id := id is ambiguous because a) the sentence if a then if b then c:= d has two parse trees b) the left most and right most derivations of the sentence if a then if b then c:= d give rise to different parse trees c) the sentence if a then if b then c:= d else c:= f has more than two parse trees d) the sentence if a then if b then c:= d else c:= f has two parse trees
• Let L1 be a regular language, L2 be a deterministic context-free language and L3 a recursively enumerable, but not recursive, language. Which one of the following statements is false?
• Let L1 be a recursive language, and let L2 be a recursively enumerable but not a recursive language. Which one of the following is TRUE?
• Let L1 be a recursive language. Let L2 and L3 be languages that are recursively enumerable but not recursive. Which of the following statements is not necessarily true?
• Which of the following problems are decidable? 1) Does a given program ever produce an output? 2) If L is a context-free language, then is L’ (complement of L) also context-free? 3) If L is a regular language, then is L’ also regular? 4) If L is a recursive language, then, is L’ also recursive?
• Which of the following macros can put a micro assembler into an infinite loop? (i) .MACRO M1 X .IF EQ, X ;if X=0 then M1 X + 1 .ENDC .IF NE X ;IF X≠0 then .WORD X ;address (X) is stored here .ENDC .ENDM (ii) .MACRO M2 X .IF EQ X M2 X .ENDC .IF NE, X .WORD X+1 .ENDC .ENDM
• Let L = L1 \cap L2, where L1 and L2 are languages as defined below: L1 = {a^{m}b^{m}ca^{n}b^{n} | m, n >= 0 } L2 = {a^{i}b^{j}c^{k} | i, j, k >= 0 } Then L is
• If s is a string over (0 + 1)* then let n0 (s) denote the number of 0’s in s and n1 (s)the number of l’s in s. Which one of the following languages is not regular?
• Let <M> be the encoding of a Turing machine as a string over ∑= {0, 1}. Let L = { <M> |M is a Turing machine that accepts a string of length 2014 }. Then, L is
• Consider the language L1,L2,L3 as given below. L1={0^{p}1^{q} | p,q \in N} L2={0^{p}1^{q} | p,q \in N and p=q} L3={0^{p}1^{q}1^{r} | p,q,r \in N and p=q=r} Which of the following statements is NOT TRUE?