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package com.wcohen.ss;
import com.wcohen.ss.api.*;
import java.util.*;
/**
* Abstract class which implements StringDistanceLearner as well as StringDistance.
* The abstract class provides default implementations of most of the StringDistanceLearner
* functions, making it easy to implement StringDistances which do little or no
* learning.
*/
public abstract class AbstractStringDistance implements StringDistance,StringDistanceLearner
{
//
// implement StringDistance
//
/** This method needs to be implemented by subclasses.
*/
abstract public double score(StringWrapper s,StringWrapper t);
/** This method needs to be implemented by subclasses.
*/
abstract public String explainScore(StringWrapper s, StringWrapper t);
/** Strings are scored by converting them to StringWrappers with the
* prepare function. */
final public double score(String s, String t) {
return score(prepare(s), prepare(t));
}
/** Scores are explained by converting Strings to StringWrappers
* with the prepare function. */
final public String explainScore(String s, String t) {
return explainScore(prepare(s),prepare(t));
}
/** Default way to preprocess a string for distance computation. If
* this is an expensive operations, then override this method to
* return a StringWrapper implementation that caches appropriate
* information about s.
*/
public StringWrapper prepare(String s) {
return new BasicStringWrapper(s);
}
//
// implement StringDistanceLearner
//
/** Implements the StringDistanceLearner api, by providing a way to
* accumulate statistics for a set of related strings. This is for
* distance metrics like TFIDF that use statistics on unlabeled
* strings to adjust a distance metric. The Default is to do
* nothing; override this method if it's necessary to accumulate
* statistics.
*/
public void setStringWrapperPool(StringWrapperIterator i) {
/* Do nothing. */ ;
}
/** Implements StringDistanceLearner api by providing a way to
* accept a pool of unlabeled DistanceInstance's. Default is
* to not use this information.
*/
public void setDistanceInstancePool(DistanceInstanceIterator i) {
/* Do nothing */;
}
/** Implements StringDistanceLearner api by informing a teacher
* if the learner has DistanceInstance queries. Default
* is to make no queries.
*/
public boolean hasNextQuery() {
return false;
}
/** Implements StringDistanceLearner api by querying for
* DistanceInstance labels.
*/
public DistanceInstance nextQuery() {
return null;
}
/** Implements StringDistanceLearner api by accepting new
* DistanceInstance labels.
*/
public void addExample(DistanceInstance answeredQuery) {
/* do nothing */;
}
/** Implements StringDistanceLearner api by providing a way to prep a
* StringWrapperIterator for training. By default this makes no
* changes to the iterator. */
public StringWrapperIterator prepare(StringWrapperIterator i) {
return i;
}
/** Implements StringDistanceLearner api by providing a way to prep a
* DistanceInstanceIterator for training. By default this makes no
* changes to the iterator. */
public DistanceInstanceIterator prepare(DistanceInstanceIterator i) {
return i;
}
/** Implements the StringDistanceLearner api by return a StringDistance.
* By default, returns this object, which also implements StringDistance.
*/
public StringDistance getDistance() { return this; }
/** Default main routine for testing */
final protected static void doMain(StringDistance d,String[] argv)
{
if (argv.length!=2) {
System.out.println("usage: string1 string2");
} else {
System.out.println(d.explainScore(argv[0],argv[1]));
}
}
}
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