TokenTextCharPrefix.java

/* Copyright (C) 2002 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. */




/**
	 Add the token text as a feature with value 1.0.

   @author Andrew McCallum <a href="mailto:mccallum@cs.umass.edu">mccallum@cs.umass.edu</a>
 */

package cc.mallet.pipe.tsf;

import java.io.*;

import cc.mallet.pipe.*;
import cc.mallet.types.*;

public class TokenTextCharPrefix extends Pipe implements Serializable
{
	String prefix;
	int prefixLength;

	public TokenTextCharPrefix (String prefix, int prefixLength)
	{
		this.prefix=prefix;
		this.prefixLength = prefixLength;
	}
	
	public TokenTextCharPrefix ()
	{
		this ("PREFIX=", 2);
	}

	public Instance pipe (Instance carrier)
	{
		TokenSequence ts = (TokenSequence) carrier.getData();
		for (int i = 0; i < ts.size(); i++) {
			Token t = ts.get(i);
			String s = t.getText();
			if (s.length() > prefixLength)
				t.setFeatureValue ((prefix + s.substring (0, prefixLength)), 1.0);
		}
		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.writeObject (prefix);
		out.writeInt (prefixLength);
	}
	
	private void readObject (ObjectInputStream in) throws IOException, ClassNotFoundException {
		int version = in.readInt ();
		prefix = (String) in.readObject();
		prefixLength = in.readInt ();
	}


}