Class Operations
- java.lang.Object
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- org.apache.lucene.util.automaton.Operations
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public final class Operations extends Object
Automata operations.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Field Summary
Fields Modifier and Type Field Description static intDEFAULT_DETERMINIZE_WORK_LIMITDefault maximum effort thatdeterminize(org.apache.lucene.util.automaton.Automaton, int)should spend before giving up and throwingTooComplexToDeterminizeException.static intMAX_RECURSION_LEVELMaximum level of recursion allowed in recursive operations.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static Automatoncomplement(Automaton a, int determinizeWorkLimit)Returns a (deterministic) automaton that accepts the complement of the language of the given automaton.static Automatonconcatenate(List<Automaton> l)Returns an automaton that accepts the concatenation of the languages of the given automata.static Automatonconcatenate(Automaton a1, Automaton a2)Returns an automaton that accepts the concatenation of the languages of the given automata.static Automatondeterminize(Automaton a, int workLimit)Determinizes the given automaton.static StringgetCommonPrefix(Automaton a)Returns the longest string that is a prefix of all accepted strings and visits each state at most once.static BytesRefgetCommonPrefixBytesRef(Automaton a)Returns the longest BytesRef that is a prefix of all accepted strings and visits each state at most once.static BytesRefgetCommonSuffixBytesRef(Automaton a)Returns the longest BytesRef that is a suffix of all accepted strings.static IntsRefgetSingleton(Automaton a)If this automaton accepts a single input, return it.static booleanhasDeadStates(Automaton a)Returns true if this automaton has any states that cannot be reached from the initial state or cannot reach an accept state.static booleanhasDeadStatesFromInitial(Automaton a)Returns true if there are dead states reachable from an initial state.static booleanhasDeadStatesToAccept(Automaton a)Returns true if there are dead states that reach an accept state.static Automatonintersection(Automaton a1, Automaton a2)Returns an automaton that accepts the intersection of the languages of the given automata.static booleanisEmpty(Automaton a)Returns true if the given automaton accepts no strings.static booleanisFinite(Automaton a)Returns true if the language of this automaton is finite.static booleanisTotal(Automaton a)Returns true if the given automaton accepts all strings.static booleanisTotal(Automaton a, int minAlphabet, int maxAlphabet)Returns true if the given automaton accepts all strings for the specified min/max range of the alphabet.static Automatonminus(Automaton a1, Automaton a2, int determinizeWorkLimit)Returns a (deterministic) automaton that accepts the intersection of the language ofa1and the complement of the language ofa2.static Automatonoptional(Automaton a)Returns an automaton that accepts the union of the empty string and the language of the given automaton.static AutomatonremoveDeadStates(Automaton a)Removes transitions to dead states (a state is "dead" if it is not reachable from the initial state or no accept state is reachable from it.)static Automatonrepeat(Automaton a)Returns an automaton that accepts the Kleene star (zero or more concatenated repetitions) of the language of the given automaton.static Automatonrepeat(Automaton a, int count)Returns an automaton that acceptsminor more concatenated repetitions of the language of the given automaton.static Automatonrepeat(Automaton a, int min, int max)Returns an automaton that accepts betweenminandmax(including both) concatenated repetitions of the language of the given automaton.static Automatonreverse(Automaton a)Returns an automaton accepting the reverse language.static Automatonreverse(Automaton a, Set<Integer> initialStates)Reverses the automaton, returning the new initial states.static booleanrun(Automaton a, String s)Returns true if the given string is accepted by the automaton.static booleanrun(Automaton a, IntsRef s)Returns true if the given string (expressed as unicode codepoints) is accepted by the automaton.static booleansameLanguage(Automaton a1, Automaton a2)Returns true if these two automata accept exactly the same language.static booleansubsetOf(Automaton a1, Automaton a2)Returns true if the language ofa1is a subset of the language ofa2.static int[]topoSortStates(Automaton a)Returns the topological sort of all states reachable from the initial state.static Automatonunion(Collection<Automaton> l)Returns an automaton that accepts the union of the languages of the given automata.static Automatonunion(Automaton a1, Automaton a2)Returns an automaton that accepts the union of the languages of the given automata.
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Field Detail
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DEFAULT_DETERMINIZE_WORK_LIMIT
public static final int DEFAULT_DETERMINIZE_WORK_LIMIT
Default maximum effort thatdeterminize(org.apache.lucene.util.automaton.Automaton, int)should spend before giving up and throwingTooComplexToDeterminizeException.- See Also:
- Constant Field Values
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MAX_RECURSION_LEVEL
public static final int MAX_RECURSION_LEVEL
Maximum level of recursion allowed in recursive operations.- See Also:
- Constant Field Values
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Method Detail
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concatenate
public static Automaton concatenate(Automaton a1, Automaton a2)
Returns an automaton that accepts the concatenation of the languages of the given automata.Complexity: linear in total number of states.
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concatenate
public static Automaton concatenate(List<Automaton> l)
Returns an automaton that accepts the concatenation of the languages of the given automata.Complexity: linear in total number of states.
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optional
public static Automaton optional(Automaton a)
Returns an automaton that accepts the union of the empty string and the language of the given automaton. This may create a dead state.Complexity: linear in number of states.
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repeat
public static Automaton repeat(Automaton a)
Returns an automaton that accepts the Kleene star (zero or more concatenated repetitions) of the language of the given automaton. Never modifies the input automaton language.Complexity: linear in number of states.
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repeat
public static Automaton repeat(Automaton a, int count)
Returns an automaton that acceptsminor more concatenated repetitions of the language of the given automaton.Complexity: linear in number of states and in
min.
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repeat
public static Automaton repeat(Automaton a, int min, int max)
Returns an automaton that accepts betweenminandmax(including both) concatenated repetitions of the language of the given automaton.Complexity: linear in number of states and in
minandmax.
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complement
public static Automaton complement(Automaton a, int determinizeWorkLimit)
Returns a (deterministic) automaton that accepts the complement of the language of the given automaton.Complexity: linear in number of states if already deterministic and exponential otherwise.
- Parameters:
determinizeWorkLimit- maximum effort to spend determinizing the automaton. Set higher to allow more complex queries and lower to prevent memory exhaustion.DEFAULT_DETERMINIZE_WORK_LIMITis a good starting default.
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minus
public static Automaton minus(Automaton a1, Automaton a2, int determinizeWorkLimit)
Returns a (deterministic) automaton that accepts the intersection of the language ofa1and the complement of the language ofa2. As a side-effect, the automata may be determinized, if not already deterministic.Complexity: quadratic in number of states if a2 already deterministic and exponential in number of a2's states otherwise.
- Parameters:
a1- the initial automatona2- the automaton to subtractdeterminizeWorkLimit- maximum effort to spend determinizing the automaton. Set higher to allow more complex queries and lower to prevent memory exhaustion.DEFAULT_DETERMINIZE_WORK_LIMITis a good starting default.
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intersection
public static Automaton intersection(Automaton a1, Automaton a2)
Returns an automaton that accepts the intersection of the languages of the given automata. Never modifies the input automata languages.Complexity: quadratic in number of states.
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sameLanguage
public static boolean sameLanguage(Automaton a1, Automaton a2)
Returns true if these two automata accept exactly the same language. This is a costly computation! Both automata must be determinized and have no dead states!
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hasDeadStates
public static boolean hasDeadStates(Automaton a)
Returns true if this automaton has any states that cannot be reached from the initial state or cannot reach an accept state. Cost is O(numTransitions+numStates).
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hasDeadStatesFromInitial
public static boolean hasDeadStatesFromInitial(Automaton a)
Returns true if there are dead states reachable from an initial state.
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hasDeadStatesToAccept
public static boolean hasDeadStatesToAccept(Automaton a)
Returns true if there are dead states that reach an accept state.
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subsetOf
public static boolean subsetOf(Automaton a1, Automaton a2)
Returns true if the language ofa1is a subset of the language ofa2. Both automata must be determinized and must have no dead states.Complexity: quadratic in number of states.
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union
public static Automaton union(Automaton a1, Automaton a2)
Returns an automaton that accepts the union of the languages of the given automata.Complexity: linear in number of states.
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union
public static Automaton union(Collection<Automaton> l)
Returns an automaton that accepts the union of the languages of the given automata.Complexity: linear in number of states.
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determinize
public static Automaton determinize(Automaton a, int workLimit)
Determinizes the given automaton.Worst case complexity: exponential in number of states.
- Parameters:
workLimit- Maximum amount of "work" that the powerset construction will spend before throwingTooComplexToDeterminizeException. Higher numbers allow this operation to consume more memory and CPU but allow more complex automatons. UseDEFAULT_DETERMINIZE_WORK_LIMITas a decent default if you don't otherwise know what to specify.- Throws:
TooComplexToDeterminizeException- if determinizing requires more thanworkLimit"effort"
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isEmpty
public static boolean isEmpty(Automaton a)
Returns true if the given automaton accepts no strings.
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isTotal
public static boolean isTotal(Automaton a)
Returns true if the given automaton accepts all strings. The automaton must be minimized.
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isTotal
public static boolean isTotal(Automaton a, int minAlphabet, int maxAlphabet)
Returns true if the given automaton accepts all strings for the specified min/max range of the alphabet. The automaton must be minimized.
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run
public static boolean run(Automaton a, String s)
Returns true if the given string is accepted by the automaton. The input must be deterministic.Complexity: linear in the length of the string.
Note: for full performance, use the
RunAutomatonclass.
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run
public static boolean run(Automaton a, IntsRef s)
Returns true if the given string (expressed as unicode codepoints) is accepted by the automaton. The input must be deterministic.Complexity: linear in the length of the string.
Note: for full performance, use the
RunAutomatonclass.
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removeDeadStates
public static Automaton removeDeadStates(Automaton a)
Removes transitions to dead states (a state is "dead" if it is not reachable from the initial state or no accept state is reachable from it.)
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isFinite
public static boolean isFinite(Automaton a)
Returns true if the language of this automaton is finite. The automaton must not have any dead states.
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getCommonPrefix
public static String getCommonPrefix(Automaton a)
Returns the longest string that is a prefix of all accepted strings and visits each state at most once. The automaton must not have dead states. If this automaton has already been converted to UTF-8 (e.g. usingUTF32ToUTF8) then you should usegetCommonPrefixBytesRef(org.apache.lucene.util.automaton.Automaton)instead.- Returns:
- common prefix, which can be an empty (length 0) String (never null)
- Throws:
IllegalArgumentException- if the automaton has dead states reachable from the initial state.
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getCommonPrefixBytesRef
public static BytesRef getCommonPrefixBytesRef(Automaton a)
Returns the longest BytesRef that is a prefix of all accepted strings and visits each state at most once.- Returns:
- common prefix, which can be an empty (length 0) BytesRef (never null), and might possibly include a UTF-8 fragment of a full Unicode character
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getSingleton
public static IntsRef getSingleton(Automaton a)
If this automaton accepts a single input, return it. Else, return null. The automaton must be deterministic.
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getCommonSuffixBytesRef
public static BytesRef getCommonSuffixBytesRef(Automaton a)
Returns the longest BytesRef that is a suffix of all accepted strings. Worst case complexity: quadratic with number of states+transitions.- Returns:
- common suffix, which can be an empty (length 0) BytesRef (never null)
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reverse
public static Automaton reverse(Automaton a)
Returns an automaton accepting the reverse language.
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reverse
public static Automaton reverse(Automaton a, Set<Integer> initialStates)
Reverses the automaton, returning the new initial states.
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topoSortStates
public static int[] topoSortStates(Automaton a)
Returns the topological sort of all states reachable from the initial state. This method assumes that the automaton does not contain cycles, and will throw an IllegalArgumentException if a cycle is detected. The CPU cost is O(numTransitions), and the implementation is non-recursive, so it will not exhaust the java stack for automaton matching long strings. If there are dead states in the automaton, they will be removed from the returned array.Note: This method uses a deque to iterative the states, which could potentially consume a lot of heap space for some automatons. Specifically, automatons with a deep level of states (i.e., a large number of transitions from the initial state to the final state) may particularly contribute to high memory usage. The memory consumption of this method can be considered as O(N), where N is the depth of the automaton (the maximum number of transitions from the initial state to any state). However, as this method detects cycles, it will never attempt to use infinite RAM.
- Parameters:
a- the Automaton to be sorted- Returns:
- the topologically sorted array of state ids
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