Package jflex

Class NFA

java.lang.Object
jflex.NFA
public final class NFA extends Object
Non-deterministic finite automata representation in JFlex.

Contains algorithms RegExp → NFA and NFA → DFA.

Version:
JFlex 1.7.0

  • Field Details

    • table

      StateSet[][] table
      table[current_state][next_char] is the set of states that can be reached from current_state with an input next_char

    • epsilon

      StateSet[] epsilon
      epsilon[current_state] is the set of states that can be reached from current_state via epsilon edges

    • isFinal

      boolean[] isFinal
      isFinal[state] == true invalid input: '<'=> state is a final state of the NFA

    • action

      Action[] action
      action[current_state]: the action associated with the state current_state (null, if there is no action for the state)

    • numStates

      int numStates
      the number of states in this NFA

    • numInput

      int numInput
      the current maximum number of input characters

    • numLexStates

      int numLexStates
      the number of lexical States. Lexical states have the indices 0..numLexStates-1 in the transition table

    • estSize

      int estSize
      estimated size of the NFA (before actual construction)

    • macros

      Macros macros

    • classes

      CharClasses classes

    • scanner

      LexScan scanner

    • regExps

      RegExps regExps

    • states

      private static StateSetEnumerator states

    • tempStateSet

      private static StateSet tempStateSet

    • live

      private boolean[] live

    • visited

      private boolean[] visited

  • Constructor Details

    • NFA

      public NFA(int numInput, int estSize)
      Constructor for NFA.

    • NFA

      public NFA(int numInput, LexScan scanner, RegExps regExps, Macros macros, CharClasses classes)
      Construct new NFA.

      Assumes that lookahead cases and numbers are already resolved in RegExps.

      Parameters:
      numInput - a int.
      scanner - a LexScan object.
      regExps - a RegExps object.
      macros - a Macros object.
      classes - a CharClasses object.
      See Also:

  • Method Details

    • numEntryStates

      public int numEntryStates()
      numEntryStates.
      Returns:
      a int.

    • addStandaloneRule

      public void addStandaloneRule()
      Add a standalone rule that has minimum priority, fires a transition on all single input characters and has a "print yytext" action.

    • addRegExp

      public void addRegExp(int regExpNum)
      Add a regexp to this NFA.
      Parameters:
      regExpNum - the number of the regexp to add.

    • insertLookAheadChoices

      private void insertLookAheadChoices(int baseEnd, Action a, RegExp lookAhead)
      Insert NFAs for the (finitely many) fixed length lookahead choices.
      Parameters:
      baseEnd - the end state of the base expression NFA
      a - the action of the expression
      lookAhead - a lookahead of which isFiniteChoice is true
      See Also:

    • ensureCapacity

      private void ensureCapacity(int newNumStates)
      Make sure the NFA can contain at least newNumStates states.
      Parameters:
      newNumStates - the minimu number of states.

    • addTransition

      public void addTransition(int start, int input, int dest)
      addTransition.
      Parameters:
      start - a int.
      input - a int.
      dest - a int.

    • addEpsilonTransition

      public void addEpsilonTransition(int start, int dest)
      addEpsilonTransition.
      Parameters:
      start - a int.
      dest - a int.

    • containsFinal

      private boolean containsFinal(StateSet set)
      Returns true, iff the specified set of states contains a final state.
      Parameters:
      set - the set of states that is tested for final states.

    • getAction

      private Action getAction(StateSet set)
      Returns the action with highest priority in the specified set of states.
      Parameters:
      set - the set of states for which to determine the action

    • closure

      private StateSet closure(int startState)
      Calculates the epsilon closure for a specified set of states.

      The epsilon closure for set a is the set of states that can be reached by epsilon edges from a.

      Parameters:
      startState - the start state for the set of states to calculate the epsilon closure for
      Returns:
      the epsilon closure of the specified set of states in this NFA

    • closure

      private StateSet closure(StateSet startStates)
      Returns the epsilon closure of a set of states

    • epsilonFill

      private void epsilonFill()

    • DFAEdge

      private StateSet DFAEdge(StateSet start, int input)
      Calculates the set of states that can be reached from another set of states start with an specified input character input
      Parameters:
      start - the set of states to start from
      input - the input character for which to search the next states
      Returns:
      the set of states that are reached from start via input

    • getDFA

      public DFA getDFA()
      Returns an DFA that accepts the same language as this NFA. This DFA is usually not minimal.
      Returns:
      a DFA object.

    • dumpTable

      public void dumpTable()
      dumpTable.

    • toString

      public String toString()
      toString.
      Overrides:
      toString in class Object
      Returns:
      a String object.

    • writeDot

      public void writeDot(File file)
      writeDot.
      Parameters:
      file - a File object.

    • dotFormat

      public String dotFormat()
      dotFormat.
      Returns:
      a String object.

    • insertLetterNFA

      private void insertLetterNFA(boolean caseless, int ch, int start, int end)

    • insertStringNFA

      private IntPair insertStringNFA(boolean caseless, String str)

    • insertClassNFA

      private void insertClassNFA(List<Interval> intervals, int start, int end)

    • insertNotClassNFA

      private void insertNotClassNFA(List<Interval> intervals, int start, int end)

    • complement

      private IntPair complement(IntPair nfa)
      Constructs an NFA accepting the complement of the language of a given NFA.

      Converts the NFA into a DFA, then negates that DFA. Exponential state blowup possible and common.

      Parameters:
      nfa - the NFA to construct the complement for.
      Returns:
      a pair of integers denoting the index of start and end state of the complement NFA.

    • removeDead

      private void removeDead(int start, int end)

    • insertCCLNFA

      private void insertCCLNFA(RegExp regExp, int start, int end)
      Constructs a two state NFA for char class regexps, such that the NFA has

      exactly one start state, exactly one end state, no transitions leading out of the end state no transitions leading into the start state

      Assumes that regExp.isCharClass(macros) == true

      Parameters:
      regExp - the regular expression to construct the NFA for

    • insertNFA

      public IntPair insertNFA(RegExp regExp)
      Constructs an NFA for regExp such that the NFA has

      exactly one start state, exactly one end state, no transitions leading out of the end state no transitions leading into the start state

      Parameters:
      regExp - the regular expression to construct the NFA for
      Returns:
      a pair of integers denoting the index of start and end state of the NFA.