java.lang.Object
- org.apache.pinot.segment.local.utils.nativefst.automaton.Automaton

All Implemented Interfaces:

Serializable, Cloneable
```
public class Automaton
extends Object
implements Serializable, Cloneable
```
Finite-state automaton with regular expression operations.
Class invariants:
- An automaton is either represented explicitly (with State and Transition objects) or with a singleton string (expandSingleton()) in case the automaton is known to accept exactly one string. (Implicitly, all states and transitions of an automaton are reachable from its initial state.)
- Automata are always reduced (see reduce()) and have no transitions to dead states (see removeDeadTransitions()).
- Automata provided as input to operations are generally assumed to be disjoint.
See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field	Description
`static boolean`	`_allowMutation`	Selects whether operations may modify the input automata (default: `false`).
`static int`	`_minimization`	Selects minimization algorithm (default: `MINIMIZE_HOPCROFT`).
`static boolean`	`_minimizeAlways`	Minimize always flag.
`static int`	`MINIMIZE_BRZOZOWSKI`	Minimize using Brzozowski's O(2ⁿ) algorithm.
`static int`	`MINIMIZE_HOPCROFT`	Minimize using Hopcroft's O(n log n) algorithm.
`static int`	`MINIMIZE_HUFFMAN`	Minimize using Huffman's O(n²) algorithm.
`static int`	`MINIMIZE_VALMARI`	Minimize using Valmari's O(n + m log m) algorithm.

Constructor Summary

Constructors
Constructor Description

Automaton()
Constructs a new automaton that accepts the empty language.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`addEpsilons(Collection<StatePair> pairs)`	See `BasicOperations.addEpsilons(Automaton, Collection)`.
`Automaton`	`clone()`	Returns a clone of this automaton.
`Automaton`	`complement()`	See `BasicOperations.complement(Automaton)`.
`void`	`determinize()`	See `BasicOperations.determinize(Automaton)`.
`boolean`	`equals(Object obj)`	Returns true if the language of this automaton is equal to the language of the given automaton.
`void`	`expandSingleton()`	Expands singleton representation to normal representation.
`Set<State>`	`getAcceptStates()`	Returns the set of reachable accept states.
`State`	`getInitialState()`	Gets initial state.
`int`	`getNumberOfStates()`	Returns the number of states in this automaton.
`int`	`getNumberOfTransitions()`	Returns the number of transitions in this automaton.
`Set<State>`	`getStates()`	Returns the set of states that are reachable from the initial state.
`int`	`hashCode()`	Returns hash code for this automaton.
`Automaton`	`intersection(Automaton a)`	See `BasicOperations.intersection(Automaton, Automaton)`.
`boolean`	`isEmpty()`	See `BasicOperations.isEmpty(Automaton)`.
`boolean`	`isEmptyString()`	See `BasicOperations.isEmptyString(Automaton)`.
`void`	`minimize()`	See `MinimizationOperations.minimize(Automaton)`.
`static Automaton`	`minimize(Automaton a)`	See `MinimizationOperations.minimize(Automaton)`.
`Automaton`	`minus(Automaton a)`	See `BasicOperations.minus(Automaton, Automaton)`.
`Automaton`	`optional()`	See `BasicOperations.optional(Automaton)`.
`void`	`reduce()`	Reduces this automaton.
`void`	`removeDeadTransitions()`	Removes transitions to dead states and calls `reduce()` and `clearHashCode()`.
`Automaton`	`repeat()`	See `BasicOperations.repeat(Automaton)`.
`Automaton`	`repeat(int min)`	See `BasicOperations.repeat(Automaton, int)`.
`Automaton`	`repeat(int min, int max)`	See `BasicOperations.repeat(Automaton, int, int)`.
`boolean`	`run(String s)`	See `BasicOperations.run(Automaton, String)`.
`static boolean`	`setAllowMutate(boolean flag)`	Sets or resets allow mutate flag.
`void`	`setInitialState(State s)`	Sets initial state.
`boolean`	`subsetOf(Automaton a)`	See `BasicOperations.subsetOf(Automaton, Automaton)`.
`String`	`toString()`	Returns a string representation of this automaton.

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - MINIMIZE_HUFFMAN
```
public static final int MINIMIZE_HUFFMAN
```
    Minimize using Huffman's O(n²) algorithm. This is the standard text-book algorithm.
    
    See Also:
    
    Constant Field Values
  - MINIMIZE_BRZOZOWSKI
```
public static final int MINIMIZE_BRZOZOWSKI
```
    Minimize using Brzozowski's O(2ⁿ) algorithm. This algorithm uses the reverse-determinize-reverse-determinize trick, which has a bad worst-case behavior but often works very well in practice (even better than Hopcroft's!).
    
    See Also:
    
    Constant Field Values
  - MINIMIZE_HOPCROFT
```
public static final int MINIMIZE_HOPCROFT
```
    Minimize using Hopcroft's O(n log n) algorithm.
    
    See Also:
    
    Constant Field Values
  - MINIMIZE_VALMARI
```
public static final int MINIMIZE_VALMARI
```
    Minimize using Valmari's O(n + m log m) algorithm.
    
    See Also:
    
    Constant Field Values
  - _minimizeAlways
```
public static boolean _minimizeAlways
```
    Minimize always flag.
  - _allowMutation
```
public static boolean _allowMutation
```
    Selects whether operations may modify the input automata (default: false).
  - _minimization
```
public static int _minimization
```
    Selects minimization algorithm (default: MINIMIZE_HOPCROFT).
- Constructor Detail
  - Automaton
```
public Automaton()
```
    Constructs a new automaton that accepts the empty language. Using this constructor, automata can be constructed manually from State and Transition objects.
    
    See Also:
    
    setInitialState(State), State, Transition
- Method Detail
  - setAllowMutate
```
public static boolean setAllowMutate(boolean flag)
```
    Sets or resets allow mutate flag. If this flag is set, then all automata operations may modify automata given as input; otherwise, operations will always leave input automata languages unmodified. By default, the flag is not set.
    
    Parameters:
    
    flag - if true, the flag is set
    
    Returns:
    
    previous value of the flag
  - minimize
```
public static Automaton minimize(Automaton a)
```
    See MinimizationOperations.minimize(Automaton). Returns the automaton being given as argument.
  - getInitialState
```
public State getInitialState()
```
    Gets initial state.
    
    Returns:
    
    state
  - setInitialState
```
public void setInitialState(State s)
```
    Sets initial state.
    
    Parameters:
    
    s - state
  - getStates
```
public Set<State> getStates()
```
    Returns the set of states that are reachable from the initial state.
    
    Returns:
    
    set of State objects
  - getAcceptStates
```
public Set<State> getAcceptStates()
```
    Returns the set of reachable accept states.
    
    Returns:
    
    set of State objects
  - reduce
```
public void reduce()
```
    Reduces this automaton. An automaton is "reduced" by combining overlapping and adjacent edge intervals with same destination.
  - removeDeadTransitions
```
public void removeDeadTransitions()
```
    Removes transitions to dead states and calls reduce() and clearHashCode(). (A state is "dead" if no accept state is reachable from it.)
  - expandSingleton
```
public void expandSingleton()
```
    Expands singleton representation to normal representation. Does nothing if not in singleton representation.
  - getNumberOfStates
```
public int getNumberOfStates()
```
    Returns the number of states in this automaton.
  - getNumberOfTransitions
```
public int getNumberOfTransitions()
```
    Returns the number of transitions in this automaton. This number is counted as the total number of edges, where one edge may be a character interval.
  - equals
```
public boolean equals(Object obj)
```
    Returns true if the language of this automaton is equal to the language of the given automaton. Implemented using hashCode and subsetOf.
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Returns hash code for this automaton. The hash code is based on the number of states and transitions in the minimized automaton. Invoking this method may involve minimizing the automaton.
    
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Returns a string representation of this automaton.
    
    Overrides:
    
    toString in class Object
  - clone
```
public Automaton clone()
```
    Returns a clone of this automaton.
    
    Overrides:
    
    clone in class Object
  - optional
```
public Automaton optional()
```
    See BasicOperations.optional(Automaton).
  - repeat
```
public Automaton repeat()
```
    See BasicOperations.repeat(Automaton).
  - repeat
```
public Automaton repeat(int min)
```
    See BasicOperations.repeat(Automaton, int).
  - repeat
```
public Automaton repeat(int min,
                        int max)
```
    See BasicOperations.repeat(Automaton, int, int).
  - complement
```
public Automaton complement()
```
    See BasicOperations.complement(Automaton).
  - minus
```
public Automaton minus(Automaton a)
```
    See BasicOperations.minus(Automaton, Automaton).
  - intersection
```
public Automaton intersection(Automaton a)
```
    See BasicOperations.intersection(Automaton, Automaton).
  - subsetOf
```
public boolean subsetOf(Automaton a)
```
    See BasicOperations.subsetOf(Automaton, Automaton).
  - determinize
```
public void determinize()
```
    See BasicOperations.determinize(Automaton).
  - addEpsilons
```
public void addEpsilons(Collection<StatePair> pairs)
```
    See BasicOperations.addEpsilons(Automaton, Collection).
  - isEmptyString
```
public boolean isEmptyString()
```
    See BasicOperations.isEmptyString(Automaton).
  - isEmpty
```
public boolean isEmpty()
```
    See BasicOperations.isEmpty(Automaton).
  - run
```
public boolean run(String s)
```
    See BasicOperations.run(Automaton, String).
  - minimize
```
public void minimize()
```
    See MinimizationOperations.minimize(Automaton).

Class Automaton

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MINIMIZE_HUFFMAN

MINIMIZE_BRZOZOWSKI

MINIMIZE_HOPCROFT

MINIMIZE_VALMARI

_minimizeAlways

_allowMutation

_minimization

Constructor Detail

Automaton

Method Detail

setAllowMutate

minimize

getInitialState

setInitialState

getStates

getAcceptStates

reduce

removeDeadTransitions

expandSingleton

getNumberOfStates

getNumberOfTransitions

equals

hashCode

toString

clone

optional

repeat

repeat

repeat

complement

minus

intersection

subsetOf

determinize

addEpsilons

isEmptyString

isEmpty

run

minimize