org.nineml.coffeegrinder.trees

Class PriorityAxe

java.lang.Object

org.nineml.coffeegrinder.trees.PriorityAxe

All Implemented Interfaces:

Axe

public class PriorityAxe
extends java.lang.Object
implements Axe

An Axe that returns the highest priority trees first.

Constructor Summary

Constructors

Constructor and Description
PriorityAxe()
PriorityAxe(boolean avoidLoops)

Method Summary

Modifier and Type	Method and Description
void	forArborist(Arborist arborist) Who's using this axe?
boolean	isSpecialist() Is this a specialist axe?
java.util.List<Family>	select(ParseTree tree, ForestNode node, int count, java.util.List<Family> choices) Select a branch from a list of branches.
boolean	wasAmbiguousSelection() Was the previous selection ambiguous?

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PriorityAxe

public PriorityAxe()

PriorityAxe

public PriorityAxe(boolean avoidLoops)

Method Detail

isSpecialist

public boolean isSpecialist()

Description copied from interface: Axe

Is this a specialist axe?

A specialist axe can consider every tree in the forest differently every time it is used. A non-specialist axe considers every tree at most once and returns all the trees that are selected.

Specified by:

isSpecialist in interface Axe

Returns:

true if the axe is specialist

select

public java.util.List<Family> select(ParseTree tree,
                                     ForestNode node,
                                     int count,
                                     java.util.List<Family> choices)

Description copied from interface: Axe

Select a branch from a list of branches.

In an ambiguous forest, some nodes will have more than one possible choice. In any given tree, only one choice may be selected. This function is called to make the selection.

There will always be at least one element in the choices list when the method is called. The method must return at least one.

The first node in the list returned is the choice selected for the tree currently under construction. If only one choice is returned, the node becomes unambiguous on subsequent parses, the same selection will always be used. If additional choices are returned, they will be considered on subsequent parses. Note that if you want the selected choice to be considered on future parses, it must appear in the list twice. It is the only node that may appear twice.

Specified by:

select in interface Axe

Parameters:

tree - the parent node in the parse tree

node - the forest node

count - the number of times node has occurred in this parse

choices - the possible paths

Returns:

the acceptable paths

wasAmbiguousSelection

public boolean wasAmbiguousSelection()

Description copied from interface: Axe

Was the previous selection ambiguous?

This method asks if the previous selection was ambiguous. If the axe ever indicates that an ambiguous selection was made, the resulting parse is considered ambiguous. For example, the SequentialAxe always returns true because it treats all choices as equivalent. The PriorityAxe only considers a selection ambiguous if there wasn't a uniquely highest priority selection.

Specified by:

wasAmbiguousSelection in interface Axe

Returns:

true if the choice made was random

forArborist

public void forArborist(Arborist arborist)

Description copied from interface: Axe

Who's using this axe?

Do not pass the same axe to more than one Arborist.

Specified by:

forArborist in interface Axe

Parameters:

arborist - the Arborist using this axe.