package edu.northwestern.at.utils.corpuslinguistics.lemmatizer;
/* Please see the license information at the end of this file. */
import java.util.*;
import java.util.regex.*;
import edu.northwestern.at.utils.*;
/** A Lemmatizer Rule which uses regular expressions.
*
* <p>
* A lemmarizer rule specifies a string substitution pattern
* used as part of the process of reducing an elaborated
* morphological form to its base form (lemma).
* </p>
*/
public class DefaultLemmatizerRule implements LemmatizerRule
{
/** Original rule text. */
protected String ruleText;
/** Source pattern string to match. */
protected String source;
/** Compiled source pattern matcher. */
protected Pattern compiledSource;
/** Replacement string. */
protected String replacement;
/** Compiled VCR string matcher. */
protected static final Pattern VCRMatcher =
Pattern.compile( "([VCRA]+)" );
/** Match direction (LEFT or RIGHT). */
public static final int LEFT = 0;
public static final int RIGHT = 1;
protected int direction;
/** Minimum match length. */
protected int matchLength;
/** Must match dictionary entry. */
protected boolean mustMatchDictionaryEntry;
/** Create a lemmatizer rule.
*
* @param ruleText The rule text.
*/
public DefaultLemmatizerRule( String ruleText )
{
this.ruleText = ruleText;
direction = RIGHT;
source = "";
replacement = "";
mustMatchDictionaryEntry = false;
StringTokenizer tokenizer =
new StringTokenizer( ruleText , " \t" );
int nTokens = tokenizer.countTokens();
if ( nTokens > 0 )
{
String[] tokens = new String[ nTokens ];
for ( int i = 0 ; i < nTokens ; i++ )
{
tokens[ i ] = tokenizer.nextToken();
}
int i = 0;
char ch = tokens[ 0 ].charAt( 0 );
switch( ch )
{
case '<' :
case '>' :
direction = ( ch == '<' ? LEFT : RIGHT );
matchLength =
StringUtils.stringToInt
(
tokens[ 0 ].substring( 1 ) ,
0
);
i++;
break;
case '+' :
mustMatchDictionaryEntry = true;
i++;
break;
default : ;
}
source = tokens[ i++ ];
if ( i < nTokens )
{
replacement = tokens[ i ];
}
int replacementCount = 1;
if ( matchLength > 0 )
{
if ( direction == RIGHT )
{
source = "(..)" + source;
replacement = "$" + replacementCount + replacement;
replacementCount++;
}
else
{
matchLength--;
source = "^(.{1," + matchLength + "})" + source;
replacement = "$" + replacementCount + replacement;
replacementCount++;
}
}
Matcher m = VCRMatcher.matcher( source );
if ( source.indexOf( "CC" ) >= 0 )
{
source =
StringUtils.replaceAll
(
source ,
"CC" ,
"([^aeiouy])\\1"
);
replacement =
StringUtils.replaceFirst
(
replacement ,
"C" ,
"$" + replacementCount
);
}
else if ( m.find() )
{
String phonolog = m.group( 1 );
int start = m.start();
int end = m.end();
source =
source.substring( 0 , start ) + "(" +
phonolog + ")" +
source.substring( end );
source =
// StringUtils.replaceAll( source , "V" , "[aeiouyr]" );
StringUtils.replaceAll( source , "V" , "[aeiouy]" );
source =
StringUtils.replaceAll( source , "C" , "[^aeiouy]" );
source =
StringUtils.replaceAll( source , "R" , "r" );
source =
StringUtils.replaceAll( source , "A" , ".*" );
replacement =
StringUtils.replaceFirst
(
replacement ,
phonolog ,
"$" + replacementCount
);
replacementCount++;
}
source = source + "$";
compiledSource = Pattern.compile( source );
}
}
/** Apply a lemmatization rule to a string.
*
* @param s String to which to apply rule.
* @param dictionary List of known words.
*
* @return String after rule applied.
*/
public String apply( String s , Set<String> dictionary )
{
String result = s;
if ( compiledSource != null )
{
Matcher m = compiledSource.matcher( s );
if ( m.find() )
{
result = m.replaceAll( replacement );
if ( mustMatchDictionaryEntry )
{
if ( !dictionary.contains( result.toLowerCase() ) )
{
result = s;
}
}
}
}
return result;
}
/** Apply a lemmatization rule to a string.
*
* @param s String to which to apply rule.
*
* @return String after rule applied.
*/
public String apply( String s )
{
return apply( s , null );
}
/** Return string version of rule.
*
* @return String version of rule. Dictionary lookup not marked.
*/
public String toString()
{
return "s/" + source + "/" + replacement + "/";
}
}
/*
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Northwestern University
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Software is furnished to do so, subject to the following
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