Package jflex
Class NFA
- java.lang.Object
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- jflex.NFA
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public final class NFA extends java.lang.Object
Non-deterministic finite automata representation in JFlex.Contains algorithms RegExp → NFA and NFA → DFA.
- Version:
- JFlex 1.7.0
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Field Summary
Fields Modifier and Type Field Description (package private) Action[]
action
action[current_state]: the action associated with the state current_state (null, if there is no action for the state)(package private) CharClasses
classes
(package private) StateSet[]
epsilon
epsilon[current_state] is the set of states that can be reached from current_state via epsilon edges(package private) int
estSize
estimated size of the NFA (before actual construction)(package private) boolean[]
isFinal
isFinal[state] == true <=> state is a final state of the NFAprivate boolean[]
live
(package private) Macros
macros
(package private) int
numInput
the current maximum number of input characters(package private) int
numLexStates
the number of lexical States.(package private) int
numStates
the number of states in this NFA(package private) RegExps
regExps
(package private) LexScan
scanner
private static StateSetEnumerator
states
(package private) StateSet[][]
table
table[current_state][next_char] is the set of states that can be reached from current_state with an input next_charprivate static StateSet
tempStateSet
private boolean[]
visited
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addEpsilonTransition(int start, int dest)
addEpsilonTransition.void
addRegExp(int regExpNum)
Add a regexp to this NFA.void
addStandaloneRule()
Add a standalone rule that has minimum priority, fires a transition on all single input characters and has a "print yytext" action.void
addTransition(int start, int input, int dest)
addTransition.private StateSet
closure(int startState)
Calculates the epsilon closure for a specified set of states.private StateSet
closure(StateSet startStates)
Returns the epsilon closure of a set of statesprivate IntPair
complement(IntPair nfa)
Constructs an NFA accepting the complement of the language of a given NFA.private boolean
containsFinal(StateSet set)
Returnstrue
, iff the specified set of states contains a final state.private StateSet
DFAEdge(StateSet start, int input)
Calculates the set of states that can be reached from another set of statesstart
with an specified input characterinput
java.lang.String
dotFormat()
dotFormat.void
dumpTable()
dumpTable.private void
ensureCapacity(int newNumStates)
Make sure the NFA can contain at least newNumStates states.private void
epsilonFill()
private Action
getAction(StateSet set)
Returns the action with highest priority in the specified set of states.DFA
getDFA()
Returns an DFA that accepts the same language as this NFA.private void
insertCCLNFA(RegExp regExp, int start, int end)
Constructs a two state NFA for char class regexps, such that the NFA hasprivate void
insertClassNFA(java.util.List<Interval> intervals, int start, int end)
private void
insertLetterNFA(boolean caseless, int ch, int start, int end)
private void
insertLookAheadChoices(int baseEnd, Action a, RegExp lookAhead)
Insert NFAs for the (finitely many) fixed length lookahead choices.IntPair
insertNFA(RegExp regExp)
Constructs an NFA for regExp such that the NFA hasprivate void
insertNotClassNFA(java.util.List<Interval> intervals, int start, int end)
private IntPair
insertStringNFA(boolean caseless, java.lang.String str)
int
numEntryStates()
numEntryStates.private void
removeDead(int start, int end)
java.lang.String
toString()
toString.void
writeDot(java.io.File file)
writeDot.
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Field Detail
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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
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epsilon
StateSet[] epsilon
epsilon[current_state] is the set of states that can be reached from current_state via epsilon edges
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isFinal
boolean[] isFinal
isFinal[state] == true <=> state is a final state of the NFA
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action
Action[] action
action[current_state]: the action associated with the state current_state (null, if there is no action for the state)
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numStates
int numStates
the number of states in this NFA
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numInput
int numInput
the current maximum number of input characters
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numLexStates
int numLexStates
the number of lexical States. Lexical states have the indices 0..numLexStates-1 in the transition table
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estSize
int estSize
estimated size of the NFA (before actual construction)
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macros
Macros macros
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classes
CharClasses classes
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scanner
LexScan scanner
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regExps
RegExps regExps
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states
private static StateSetEnumerator states
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tempStateSet
private static StateSet tempStateSet
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live
private boolean[] live
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visited
private boolean[] visited
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Constructor Detail
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NFA
public NFA(int numInput, int estSize)
Constructor for NFA.
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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
- aLexScan
object.regExps
- aRegExps
object.macros
- aMacros
object.classes
- aCharClasses
object.- See Also:
RegExps.checkLookAheads()
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Method Detail
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numEntryStates
public int numEntryStates()
numEntryStates.- Returns:
- a int.
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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.
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addRegExp
public void addRegExp(int regExpNum)
Add a regexp to this NFA.- Parameters:
regExpNum
- the number of the regexp to add.
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insertLookAheadChoices
private void insertLookAheadChoices(int baseEnd, Action a, RegExp lookAhead)
Insert NFAs for the (finitely many) fixed length lookahead choices.- Parameters:
lookAhead
- a lookahead of which isFiniteChoice is truebaseEnd
- the end state of the base expression NFAa
- the action of the expression- See Also:
SemCheck.isFiniteChoice(RegExp)
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ensureCapacity
private void ensureCapacity(int newNumStates)
Make sure the NFA can contain at least newNumStates states.- Parameters:
newNumStates
- the minimu number of states.
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addTransition
public void addTransition(int start, int input, int dest)
addTransition.- Parameters:
start
- a int.input
- a int.dest
- a int.
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addEpsilonTransition
public void addEpsilonTransition(int start, int dest)
addEpsilonTransition.- Parameters:
start
- a int.dest
- a int.
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containsFinal
private boolean containsFinal(StateSet set)
Returnstrue
, iff the specified set of states contains a final state.- Parameters:
set
- the set of states that is tested for final states.
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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
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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
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closure
private StateSet closure(StateSet startStates)
Returns the epsilon closure of a set of states
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epsilonFill
private void epsilonFill()
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DFAEdge
private StateSet DFAEdge(StateSet start, int input)
Calculates the set of states that can be reached from another set of statesstart
with an specified input characterinput
- Parameters:
start
- the set of states to start frominput
- the input character for which to search the next states- Returns:
- the set of states that are reached from
start
viainput
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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.
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dumpTable
public void dumpTable()
dumpTable.
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toString
public java.lang.String toString()
toString.- Overrides:
toString
in classjava.lang.Object
- Returns:
- a
String
object.
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writeDot
public void writeDot(java.io.File file)
writeDot.- Parameters:
file
- aFile
object.
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dotFormat
public java.lang.String dotFormat()
dotFormat.- Returns:
- a
String
object.
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insertLetterNFA
private void insertLetterNFA(boolean caseless, int ch, int start, int end)
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insertStringNFA
private IntPair insertStringNFA(boolean caseless, java.lang.String str)
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insertClassNFA
private void insertClassNFA(java.util.List<Interval> intervals, int start, int end)
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insertNotClassNFA
private void insertNotClassNFA(java.util.List<Interval> intervals, int start, int end)
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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.
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removeDead
private void removeDead(int start, int end)
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insertCCLNFA
private void insertCCLNFA(RegExp regExp, int start, int end)
Constructs a two state NFA for char class regexps, such that the NFA hasexactly 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
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insertNFA
public IntPair insertNFA(RegExp regExp)
Constructs an NFA for regExp such that the NFA hasexactly 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.
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