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Formal Language

Regular language⚓︎

Finite automata⚓︎

The definition of finite automata⚓︎

  1. \(Q\) : state
  2. \(\sum\) : alphabet(like action)
  3. \(\delta\) : transition function \((Q \times \sum \rightarrow Q)\)
  4. \(q_{0}\) \(\in Q\) : start state
  5. \(F \subseteq Q\) : the set of accept/final state

Accept the string⚓︎

Accept the string \(w=w_{0}...w_{n}\) when 1. \(r_{0}\) = \(q_{0}\) 2. \(\delta(r_{i},w_{i+1}) = r_{i+1}\) 3. \(r_{n} \subseteq F\)

Accept and recognize⚓︎

\(L(M) =A \rightarrow\)
\(M\) recoginze \(A\) languages or
\(M\) accept the set of all string \(A\)

A language is called a regular language if some finite automaton recognizes it.

The regular operator⚓︎

  1. Union :
    If \(\sum_{1} and \sum_{2}\) are same.
    Estabalish a machine that simultaneously track 2 machine, E.g. Cartisian product.

  2. Concatenation

  3. Star