package cc.mallet.pipe;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import cc.mallet.types.FeatureSequenceWithBigrams;
import cc.mallet.types.Instance;
import cc.mallet.types.Token;
import cc.mallet.types.TokenSequence;
import cc.mallet.util.CharSequenceLexer;
/* Copyright (C) 2005 Univ. of Massachusetts Amherst, Computer Science Dept.
This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
http://www.cs.umass.edu/~mccallum/mallet
This software is provided under the terms of the Common Public License,
version 1.0, as published by http://www.opensource.org. For further
information, see the file `LICENSE' included with this distribution. */
/** Remove tokens that contain non-alphabetic characters.
* This class is used in conjunction wtih CharSequenceLexer.LEX_NON_WHITESPACE_CLASSES
* and FeatureSequenceWithBigrams, which in turn is used by TopicalNGrams.
* @author <a href="mailto:mccallum@cs.umass.edu">Andrew McCallum</a>
*/
public class TokenSequenceRemoveNonAlpha extends Pipe {
boolean markDeletions = false;
public TokenSequenceRemoveNonAlpha (boolean markDeletions)
{
this.markDeletions = markDeletions;
}
public TokenSequenceRemoveNonAlpha ()
{
this (false);
}
public Instance pipe (Instance carrier)
{
TokenSequence ts = (TokenSequence) carrier.getData();
// xxx This doesn't seem so efficient. Perhaps have TokenSequence
// use a LinkedList, and remove Tokens from it? -?
// But a LinkedList implementation of TokenSequence would be quite inefficient -AKM
TokenSequence ret = new TokenSequence ();
Token prevToken = null;
for (int i = 0; i < ts.size(); i++) {
Token t = ts.get(i);
String s = t.getText();
if (CharSequenceLexer.LEX_ALPHA.matcher(s).matches()) {
ret.add (t);
prevToken = t;
} else if (markDeletions && prevToken != null)
prevToken.setProperty (FeatureSequenceWithBigrams.deletionMark, t.getText());
}
carrier.setData(ret);
return carrier;
}
// Serialization
private static final long serialVersionUID = 1;
private static final int CURRENT_SERIAL_VERSION = 0;
private void writeObject (ObjectOutputStream out) throws IOException {
out.writeInt (CURRENT_SERIAL_VERSION);
out.writeBoolean(markDeletions);
}
private void readObject (ObjectInputStream in) throws IOException, ClassNotFoundException {
int version = in.readInt ();
markDeletions = in.readBoolean();
}
}