Write regular expressions for the following languages over the alphabet Σ = {a, b }: Draw DFAs for each of the languages from question 1 None of your DFAs
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[PDF] Regular Expressions
Each regular expression E represents also a language L(E) If Σ = {a, b, c} The expressions (ab) ∗ represents automaton This works for DFA, NFA, ϵ-NFA
[PDF] Written Assignment 1 Solutions
Write regular expressions for the following languages over the alphabet Σ = {a, b }: Draw DFAs for each of the languages from question 1 None of your DFAs
[PDF] Regular Languages and Finite Automata-II - Department of
9 déc 2020 · 6 Regular Languages Finite Automata - Finite Automata A={a, b} The regular expression of the language of the DFA is (a + b)b* Why?
[PDF] DFA - CMSC 330: Organization of Programming Languages
alphabet Σ = {a, b, c} • L = { s s ∊ Σ* and s = 0} = {ε} ≠ Ø Example: The set of all valid Ruby programs • Is there a Ruby regular expression for this language?
[PDF] Convert Regular Expression to DFA - JFLAP
Convert Regular Expression to DFA -‐ Exercise Problem: Convert a(b+c)*a to a DFA The string must start with an a which is followed by a mix of b's and
[PDF] Homework 3 Solutions
state within this DFA state, and where the NFA can go on a b from each NFA state (b) Prove that L has a regular expression, where L is the set of strings
[PDF] Finite Automaton to Regular Expression
L1 = {a, ab, abb, abbb, , c} L2 = {ε, aa, ab, ba, abab, bbaa, baabbaabab, } We can then convert N to a DFA M recognizing L(R), so L(R) is regular regular expression formed by the sum of the labels on each of the edges from i to j 20
[PDF] Deterministic Finite Automata A d
The example DFA accepts the strings a, b, ab, bb, abb, bbb, , abn, bbn, So the language of the DFA is given by the regular expression (a + b)b* Start 0 1
[PDF] Regular Expression & NFA - Automata Theory - University of San
FR-69: Fun with NFA Create an NFA for: All strings over {a, b} that start with a and end with b (also create a DFA, and regular expression)
[PDF] Regular Expressions
We have seen that DFAs and NFAs have equal definitional power A regular expression is a string r that denotes a language L(r) over some alphabet {ab, ac} The only way to define an infinite language using regular expressions is with
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CS 143 Compilers Handout 7
Written Assignment I Solutions
1.Write regular expressions for the following languages over the alphabet Σ ={a,b}:(a)All strings that do not end withaa.
?+a+b+ (a+b)?(ab+ba+bb)(b)All strings that contain an even number ofb"s. a ?(ba?ba?)?(c)All strings which do not contain the substringba. a ?b?2.Draw DFAs for each of the languages from question 1. None of your DFAs may contain more than 4 states.(a) (b) (c)Fall 2010/2011page 1 of 3
CS 143 Compilers Handout 7
3.Consider the following non-deterministic finite automaton (NFA) over the alphabet Σ ={0,1}.Give a one-sentence description of the language recognized by the NFA. Write a regular expression for
this language.•The NFA recognizes all strings that contain two 0"s separated by a substring whose length is a
multiple of 3.•A regular expression for this language is (0 + 1) ?0((0 + 1)(0 + 1)(0 + 1))?0(0 + 1)?.4.Let Σ m={a1,...,am}be an alphabet containingmelements, for some integerm≥1. LetLmbe the following language:All strings in which at least oneaioccurs an even numberThe following figure shows an NFA for the languageL2.Construct a DFA for the languageL2that has at most 6 states. Also construct an NFA for the
languageL3that has at most 7 states. Aside:Non-deterministic finite automata (NFAs) are no more powerful than DFAs in terms of the languages that they can describe. However, NFAs can be exponentially more succinct than DFAs, as this problem demonstrates. For the languageLm, there exists an NFA of size at most 2m+1 while anyDFA must have size at least 2
m. Note that the DFA for the languageL3is not as easy to construct as the NFA for the languageL3.Fall 2010/2011page 2 of 3CS 143 Compilers Handout 7
5.Consider the string
abaabaabababbaaabaab and its tokenization abaa ba ababa bba aa ba a bGive a flex specification with the minimum number of rules that produces this tokenization. Each flex
rule should be as simple as possible as well. You may not use regular expression union (i.e.,R1+R2 )in your solution. Do not give any actions; just assume that the rule returns the string that it matches.•(ab)*a+
•b*a?