regular-expressions

A lexical analyzer uses the following token definitions letter → [A - Za - z] digit → [0-9] id → letter (letter $\mid$ digit)* number → digit $^{+}$ ws → (blank | tab | newline) ${...

Let M be the 5-state NFA with \epsilon-transitions shown in the diagram below. Which one of the following regular expressions represents the language accepted by M?

Consider the following two regular expressions over the alphabet {0,1}: r = 0* + 1* s = 01* + 10* The total number of strings of length less than or equal to 5, which are neither i...

Consider the following two regular expressions over the alphabet {0,1} : $$r = 0^* + 1^*$$ $$s = 01^* + 10^*$$ The total number of strings of length less than or equal to 5, which...

Let L 1 be the language represented by the regular expression b * ab * (ab * ab * ) * and L 2 = { w ∈ (a + b) * | |w| ≤ 4 } , where |w| denotes the length of string w . The number...

Which one of the following regular expressions represents the set of all binary strings with an odd number of 1’s?

A lexical analyzer uses the following patterns to recognize three tokens $${T_1},{T_2},$$ and $${T_3}$$ over the alphabet $$\left\{ {a,b,c} \right\}.$$ $$\eqalign{ & {T_1}:\,\,\,a?...

Which one of the following regular expressions represents the language: the set of all binary strings having two consecutive $$0s$$ and two consecutive $$1s?$$

Match the following: GROUP - 1 GROUP - 2 (P) Lexical analysis (i) Leftmost derivation (Q) Top down parsing (ii) Type checking (R) Semantic analysis (iii) Regular expressions (S) Ru...

Consider the alphabet $$\sum { = \left\{ {0,1} \right\},} $$ the null/empty string $$\lambda $$ and the sets of strings $${X_0},\,{X_1},$$ and $${X_2}$$ generated by the correspond...

The length of the shortest string NOT in the language (over $$\sum { = \left\{ {a,\,\,b} \right\}} $$) of the following regular expression is ____________. $$$a{}^ * b{}^ * \left(...

The regular expression $${0^ * }\left( {{{10}^ * }} \right){}^ * $$denotes the same set as

Let $$S$$ and $$T$$ be languages over $$\sum { = \left\{ {a,b} \right\}} $$ represented by the regular expressions $${\left( {a + {b^ * }} \right)^ * }$$ and $$\,{\left( {a + b} \r...

The string $$1101$$ does not belong to the set represented by

If the regular set $$A$$ is represented by $$A = {\left( {01 + 1} \right)^ * }$$ and the regular set $$'B'$$ is represented by $$B = \left( {{{\left( {01} \right)}^ * }{1^ * }} \ri...

Which one of the following regular expressions over $$\left\{ {0,\,\,1} \right\}$$ denotes the set of all strings not containing $$100$$ as substring?

Which two of the following four regular expressions are equivalent? (i) $${\left( {00} \right)^ * }\left( {\varepsilon + 0} \right)$$ (ii) $${\left( {00} \right)^ * }$$ (iii) $${0^...

In some programming languages, an identifier is permitted to be a letter following by any number of letters or digits. If L and D denote the sets of letters and digits respectively...

Which of the following regular expression identities are true?

Let $$r = 1\,{\left( {1 + 0} \right)^ * },s = {11^ * }\,0$$ and $$\,t = {1^ * }\,0$$ be three regular expressions. Which one of the following is true?