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Stanford Parser processes raw text in English, Chinese, German, Arabic, and French, and extracts constituency parse trees.
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package edu.stanford.nlp.trees;
import java.io.StringReader;
import java.util.List;
import edu.stanford.nlp.ling.CoreLabel;
import edu.stanford.nlp.ling.Label;
import edu.stanford.nlp.ling.LabelFactory;
import edu.stanford.nlp.util.logging.Redwood;
/**
* A {@code TreeGraphNode} is simply a {@link Tree {@code Tree}}
* with some additional functionality. For example, the
* {@code parent()} method works without searching from the root.
* Labels are always assumed to be {@link CoreLabel {@code CoreLabel}}.
*
* This class makes the horrible mistake of changing the semantics of
* equals and hashCode to go back to "==" and System.identityHashCode,
* despite the semantics of the superclass's equality.
*
* @author Bill MacCartney
*/
public class TreeGraphNode extends Tree implements HasParent {
/** A logger for this class */
private static final Redwood.RedwoodChannels log = Redwood.channels(TreeGraphNode.class);
/**
* Label for this node.
*/
private CoreLabel label;
/**
* Parent of this node.
*/
protected TreeGraphNode parent; // = null;
/**
* Children of this node.
*/
protected TreeGraphNode[] children = ZERO_TGN_CHILDREN;
/**
* For internal nodes, the head word of this subtree.
*/
private TreeGraphNode headWordNode;
/**
* A leaf node should have a zero-length array for its
* children. For efficiency, subclasses can use this array as a
* return value for children() for leaf nodes if desired. Should
* this be public instead?
*/
protected static final TreeGraphNode[] ZERO_TGN_CHILDREN = new TreeGraphNode[0];
private static final LabelFactory mlf = CoreLabel.factory();
/**
* Create a new {@code TreeGraphNode} with the supplied
* label.
*
* @param label the label for this node.
*/
public TreeGraphNode(Label label) {
this.label = (CoreLabel) mlf.newLabel(label);
}
/**
* Create a new {@code TreeGraphNode} with the supplied
* label and list of child nodes.
*
* @param label the label for this node.
* @param children the list of child {@code TreeGraphNode}s
* for this node.
*/
public TreeGraphNode(Label label, List children) {
this(label);
setChildren(children);
}
/**
* Create a new {@code TreeGraphNode} having the same tree
* structure and label values as an existing tree (but no shared
* storage). Operates recursively to construct an entire
* subtree.
*
* @param t the tree to copy
* @param parent the parent node
*/
protected TreeGraphNode(Tree t, TreeGraphNode parent) {
this.parent = parent;
Tree[] tKids = t.children();
int numKids = tKids.length;
children = new TreeGraphNode[numKids];
for (int i = 0; i < numKids; i++) {
children[i] = new TreeGraphNode(tKids[i], this);
if (t.isPreTerminal()) { // add the tags to the leaves
children[i].label.setTag(t.label().value());
}
}
this.label = (CoreLabel) mlf.newLabel(t.label());
}
/**
* Implements equality for {@code TreeGraphNode}s. Unlike
* {@code Tree}s, {@code TreeGraphNode}s should be
* considered equal only if they are ==. Implementation note:
* TODO: This should be changed via introducing a Tree interface with the current Tree and this class implementing it, since what is done here breaks the equals() contract.
*
* @param o The object to compare with
* @return Whether two things are equal
*/
@Override
public boolean equals(Object o) {
return o == this;
}
@Override
public int hashCode() {
return System.identityHashCode(this);
}
/**
* Returns the label associated with the current node, or null
* if there is no label.
*
* @return the label of the node
*/
@Override
public CoreLabel label() {
return label;
}
@Override
public void setLabel(Label label) {
if (label instanceof CoreLabel) {
this.setLabel((CoreLabel) label);
} else {
this.setLabel((CoreLabel) mlf.newLabel(label));
}
}
/**
* Sets the label associated with the current node.
*
* @param label the new label to use.
*/
public void setLabel(final CoreLabel label) {
this.label = label;
}
/**
* Get the index for the current node.
*/
public int index() {
return label.index();
}
/**
* Set the index for the current node.
*/
protected void setIndex(int index) {
label.setIndex(index);
}
/**
* Get the parent for the current node.
*/
@Override
public TreeGraphNode parent() {
return parent;
}
/**
* Set the parent for the current node.
*/
public void setParent(TreeGraphNode parent) {
this.parent = parent;
}
/**
* Returns an array of the children of this node.
*/
@Override
public TreeGraphNode[] children() {
return children;
}
/**
* Sets the children of this {@code TreeGraphNode}. If
* given {@code null}, this method sets
* the node's children to the canonical zero-length Tree[] array.
*
* @param children an array of child trees
*/
@Override
public void setChildren(Tree[] children) {
if (children == null || children.length == 0) {
this.children = ZERO_TGN_CHILDREN;
} else {
if (children instanceof TreeGraphNode[]) {
this.children = (TreeGraphNode[]) children;
for (TreeGraphNode child : this.children) {
child.setParent(this);
}
} else {
this.children = new TreeGraphNode[children.length];
for (int i = 0; i < children.length; i++) {
this.children[i] = (TreeGraphNode)children[i];
this.children[i].setParent(this);
}
}
}
}
/** {@inheritDoc} */
@Override
public void setChildren(List childTreesList) {
if (childTreesList == null || childTreesList.isEmpty()) {
setChildren(ZERO_TGN_CHILDREN);
} else {
int leng = childTreesList.size();
TreeGraphNode[] childTrees = new TreeGraphNode[leng];
childTreesList.toArray(childTrees);
setChildren(childTrees);
}
}
@Override
public Tree setChild(int i, Tree t) {
if (!(t instanceof TreeGraphNode)) {
throw new IllegalArgumentException("Horrible error");
}
((TreeGraphNode) t).setParent(this);
return super.setChild(i, t);
}
/**
* Adds a child in the ith location. Does so without overwriting
* the parent pointers of the rest of the children, which might be
* relevant in case there are add and remove operations mixed
* together.
*/
@Override
public void addChild(int i, Tree t) {
if (!(t instanceof TreeGraphNode)) {
throw new IllegalArgumentException("Horrible error");
}
((TreeGraphNode) t).setParent(this);
TreeGraphNode[] kids = this.children;
TreeGraphNode[] newKids = new TreeGraphNode[kids.length + 1];
if (i != 0) {
System.arraycopy(kids, 0, newKids, 0, i);
}
newKids[i] = (TreeGraphNode) t;
if (i != kids.length) {
System.arraycopy(kids, i, newKids, i + 1, kids.length - i);
}
this.children = newKids;
}
/**
* Removes the ith child from the TreeGraphNode. Needs to override
* the parent removeChild so it can avoid setting the parent
* pointers on the remaining children. This is useful if you want
* to add and remove children from one node to another node; this way,
* it won't matter what order you do the add and remove operations.
*/
@Override
public Tree removeChild(int i) {
TreeGraphNode[] kids = children();
TreeGraphNode kid = kids[i];
TreeGraphNode[] newKids = new TreeGraphNode[kids.length - 1];
for (int j = 0; j < newKids.length; j++) {
if (j < i) {
newKids[j] = kids[j];
} else {
newKids[j] = kids[j + 1];
}
}
this.children = newKids;
return kid;
}
/**
* Uses the specified {@link HeadFinder {@code HeadFinder}}
* to determine the heads for this node and all its descendants,
* and to store references to the head word node and head tag node
* in this node's {@link CoreLabel {@code CoreLabel}} and the
* {@code CoreLabel}s of all its descendants.
*
* Note that, in contrast to {@link Tree#percolateHeads
* {@code Tree.percolateHeads()}}, which assumes {@link
* edu.stanford.nlp.ling.CategoryWordTag
* {@code CategoryWordTag}} labels and therefore stores head
* words and head tags merely as {@code String}s, this
* method stores references to the actual nodes. This mitigates
* potential problems in sentences which contain the same word
* more than once.
*
* @param hf The headfinding algorithm to use
*/
@Override
public void percolateHeads(HeadFinder hf) {
if (isLeaf()) {
TreeGraphNode hwn = headWordNode();
if (hwn == null) {
setHeadWordNode(this);
}
} else {
for (Tree child : children()) {
child.percolateHeads(hf);
}
TreeGraphNode head = safeCast(hf.determineHead(this,parent));
if (head != null) {
TreeGraphNode hwn = head.headWordNode();
if (hwn == null && head.isLeaf()) { // below us is a leaf
setHeadWordNode(head);
} else {
setHeadWordNode(hwn);
}
} else {
log.info("Head is null: " + this);
}
}
}
/**
* Return the node containing the head word for this node (or
* {@code null} if none), as recorded in this node's {@link
* CoreLabel {@code CoreLabel}}. (In contrast to {@link
* edu.stanford.nlp.ling.CategoryWordTag
* {@code CategoryWordTag}}, we store head words and head
* tags as references to nodes, not merely as
* {@code String}s.)
*
* @return the node containing the head word for this node
*/
public TreeGraphNode headWordNode() {
return headWordNode;
}
/**
* Store the node containing the head word for this node by
* storing it in this node's {@link CoreLabel
* {@code CoreLabel}}. (In contrast to {@link
* edu.stanford.nlp.ling.CategoryWordTag
* {@code CategoryWordTag}}, we store head words and head
* tags as references to nodes, not merely as
* {@code String}s.)
*
* @param hwn the node containing the head word for this node
*/
private void setHeadWordNode(final TreeGraphNode hwn) {
this.headWordNode = hwn;
}
/**
* Safely casts an {@code Object} to a
* {@code TreeGraphNode} if possible, else returns
* {@code null}.
*
* @param t any {@code Object}
* @return {@code t} if it is a {@code TreeGraphNode};
* {@code null} otherwise
*/
private static TreeGraphNode safeCast(Object t) {
if (t == null || !(t instanceof TreeGraphNode)) {
return null;
}
return (TreeGraphNode) t;
}
/**
* Checks the node's ancestors to find the highest ancestor with the
* same {@code headWordNode} as this node.
*/
public TreeGraphNode highestNodeWithSameHead() {
TreeGraphNode node = this;
while (true) {
TreeGraphNode parent = safeCast(node.parent());
if (parent == null || parent.headWordNode() != node.headWordNode()) {
return node;
}
node = parent;
}
}
// extra class guarantees correct lazy loading (Bloch p.194)
private static class TreeFactoryHolder {
static final TreeGraphNodeFactory tgnf = new TreeGraphNodeFactory();
private TreeFactoryHolder() {
}
}
/**
* Returns a {@code TreeFactory} that produces
* {@code TreeGraphNode}s. The {@code Label} of
* {@code this} is examined, and providing it is not
* {@code null}, a {@code LabelFactory} which will
* produce that kind of {@code Label} is supplied to the
* {@code TreeFactory}. If the {@code Label} is
* {@code null}, a
* {@code CoreLabel.factory()} will be used. The factories
* returned on different calls are different: a new one is
* allocated each time.
*
* @return a factory to produce treegraphs
*/
@Override
public TreeFactory treeFactory() {
LabelFactory lf;
if (label() != null) {
lf = label().labelFactory();
} else {
lf = CoreLabel.factory();
}
return new TreeGraphNodeFactory(lf);
}
/**
* Return a {@code TreeFactory} that produces trees of type
* {@code TreeGraphNode}. The factory returned is always
* the same one (a singleton).
*
* @return a factory to produce treegraphs
*/
public static TreeFactory factory() {
return TreeFactoryHolder.tgnf;
}
/**
* Return a {@code TreeFactory} that produces trees of type
* {@code TreeGraphNode}, with the {@code Label} made
* by the supplied {@code LabelFactory}. The factory
* returned is a different one each time.
*
* @param lf The {@code LabelFactory} to use
* @return a factory to produce treegraphs
*/
public static TreeFactory factory(LabelFactory lf) {
return new TreeGraphNodeFactory(lf);
}
/**
* Returns a {@code String} representation of this node and
* its subtree with one node per line, indented according to
* {@code indentLevel}.
*
* @param indentLevel how many levels to indent (0 for root node)
* @return {@code String} representation of this subtree
*/
public String toPrettyString(int indentLevel) {
StringBuilder buf = new StringBuilder("\n");
for (int i = 0; i < indentLevel; i++) {
buf.append(" ");
}
if (children == null || children.length == 0) {
buf.append(label.toString(CoreLabel.OutputFormat.VALUE_INDEX_MAP));
} else {
buf.append('(').append(label.toString(CoreLabel.OutputFormat.VALUE_INDEX_MAP));
for (TreeGraphNode child : children) {
buf.append(' ').append(child.toPrettyString(indentLevel + 1));
}
buf.append(')');
}
return buf.toString();
}
/**
* Returns a {@code String} representation of this node and
* its subtree as a one-line parenthesized list.
*
* @return {@code String} representation of this subtree
*/
public String toOneLineString() {
StringBuilder buf = new StringBuilder();
if (children == null || children.length == 0) {
buf.append(label);
} else {
buf.append('(').append(label);
for (TreeGraphNode child : children) {
buf.append(' ').append(child.toOneLineString());
}
buf.append(')');
}
return buf.toString();
}
@Override
public String toString() {
return toString(CoreLabel.DEFAULT_FORMAT);
}
public String toString(CoreLabel.OutputFormat format) {
return label.toString(format);
}
/**
* Just for testing.
*/
public static void main(String[] args) {
try {
TreeReader tr = new PennTreeReader(new StringReader("(S (NP (NNP Sam)) (VP (VBD died) (NP (NN today))))"), new LabeledScoredTreeFactory());
Tree t = tr.readTree();
System.out.println(t);
TreeGraphNode tgn = new TreeGraphNode(t, (TreeGraphNode) null);
System.out.println(tgn.toPrettyString(0));
EnglishGrammaticalStructure gs = new EnglishGrammaticalStructure(tgn);
System.out.println(tgn.toPrettyString(0));
tgn.percolateHeads(new SemanticHeadFinder());
System.out.println(tgn.toPrettyString(0));
} catch (Exception e) {
log.error("Horrible error: " + e);
log.error(e);
}
}
private static final long serialVersionUID = 5080098143617475328L;
}
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