01-FiniteStateMachines

# Parens group regular expressions as expected examples

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Parens group regular expressions as expected Examples: (a|b)c matches …ac… and …bc… (a|b)*c matches …c… and …ac… and … bac… and … ababababbbabbabaaaababaababbbbc… and (a|b)?c matches …c… and …ac… and …bc…

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Regular Expression Extensions (e.g. Google Regular Expressions) Additional shorthand and notation [A-Z] = A|B|…|Z [ABC] = A|B|C \ is an escape character: \* matches …*… Languages and language extensions/packages Perl Java regular-expression packages Examples: Google Regular Expressions regexpal
Regular Expressions & Finite State Machines abc a(b|c) ab* (a(b?c)) + a b c Note the special double-circle designation of an accepting state. a a a b b b a c c c

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Formal Definition of a Finite State Machine & a Finite State Transducer A deterministic finite state machine is a quintuple (Σ, S , s 0 ,δ, F ), where: Σ is the input alphabet (a finite, non-empty set of symbols). S is a finite, non-empty set of states. s 0 is an initial state, an element of S . δ is the state-transition function: δ : S × Σ → S . F is the set of final states, a (possibly empty) subset of S . A finite state transducer is a 6-tuple (Σ,Γ, S , s 0 ,δ, F ) as above except: Γ is the output alphabet (a finite, non-empty set of symbols). δ is the state-transition function: δ : S × Σ → S × Γ.
Project 1: Lexical Analyzer Varieties Description Example <String> Any sequence of characters enclosed in single quotes. Two single quotes denote an apostrophe within the string. For line- number counts, count all '\n's within a string. A string token’s line number is the line where the string starts. 'quoted string' 'this isn''t two strings' '' (empty string) 'don''t forget about multi- line strings' <Keyword> One of the following four character sequences: Schemes , Facts , Rules , Queries. These keywords are case sensitive. Example: Schemesa is a single identifier and not a keyword and an identifier. <Identifier> An identifier is a letter followed by a sequence of zero or more letters or numbers. No underscores. Legal identifiers: Invalid identifiers: Identifier1 1stPerson Person Person_Name <Symbol> One of the following character sequences: : , < > = ( * ?

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• Winter '12
• MichaelGoodrich
• Regular expression, Finite State Machines, regular expressions

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