edu.stanford.nlp.parser.shiftreduce

Class State

java.lang.Object

edu.stanford.nlp.parser.shiftreduce.State

All Implemented Interfaces:

Scored

public class State
extends Object
implements Scored

A class which encodes the current state of the parsing. This can be used either for direct search or for beam search.
Important information which needs to be encoded:

• A stack. This needs to be updatable in O(1) time to keep the parser's run time linear. This is done by using a linked-list type stack in which new states are created by the push operation.
• A queue. This also needs to be updatable in O(1) time. This is accomplished by having all the states share the same list of queued items, with different states only changing an index into the queue.
• The score of the current state. This is useful in beam searches.
• Whether or not the current state is "finalized". If so, the only thing that can be done from now on is to idle.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	State.HeadPosition Used to describe the relative location of separators to the head of a subtree

Constructor Summary

Constructors

Constructor and Description
State(List<Tree> sentence) Expects a list of preterminals.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	areTransitionsEqual(State other) Whether or not the transitions that built the two states are equal.
boolean	endOfQueue()
boolean	isFinished()
double	score()
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

State

public State(List<Tree> sentence)

Expects a list of preterminals. The preterminals should be built with CoreLabels and have HeadWord and HeadTag annotations set.

Method Detail

score

public double score()

Specified by:

score in interface Scored

Returns:

The score of this thing.

isFinished

public boolean isFinished()

endOfQueue

public boolean endOfQueue()

toString

public String toString()

Overrides:

toString in class Object

areTransitionsEqual

public boolean areTransitionsEqual(State other)

Whether or not the transitions that built the two states are equal. Doesn't check anything else. Useful for training using an agenda, for example, when you know the underlying information such as the words are the same and all you care about checking is the transition sequence