package LBJ2.classify;
import LBJ2.learn.Lexicon;
import LBJ2.util.ByteString;
import LBJ2.util.ExceptionlessInputStream;
import LBJ2.util.ExceptionlessOutputStream;
/**
* A real feature takes on any value representable by a <code>double</code>.
*
* @author Nick Rizzolo
**/
public class RealPrimitiveStringFeature extends RealFeature
{
/**
* The <code>identifier</code> string distinguishes this
* <code>Feature</code> from other <code>Feature</code>s.
**/
protected String identifier;
/** The real value is represented as a double. */
protected double value;
/**
* For internal use only.
*
* @see Feature#readFeature(ExceptionlessInputStream)
**/
protected RealPrimitiveStringFeature() { }
/**
* Sets both the identifier and the value.
*
* @param p The new real feature's package.
* @param c The name of the classifier that produced this feature.
* @param i The new <code>RealPrimitiveStringFeature</code>'s identifier.
* @param v The new <code>RealPrimitiveStringFeature</code>'s value.
**/
public RealPrimitiveStringFeature(String p, String c, String i, double v) {
super(p, c);
identifier = i;
value = v;
}
/**
* Determines if this feature contains a string identifier field.
*
* @return <code>true</code> iff this feature contains a string identifier
* field.
**/
public boolean hasStringIdentifier() { return true; }
/**
* Determines if this feature is primitive.
*
* @return <code>true</code> iff this is primitive.
**/
public boolean isPrimitive() { return true; }
/**
* Retrieves this feature's identifier as a string.
*
* @return This feature's identifier as a string.
**/
public String getStringIdentifier() { return identifier; }
/**
* Retrieves this feature's identifier as a byte string.
*
* @return This feature's identifier as a byte string.
**/
public ByteString getByteStringIdentifier() {
return new ByteString(identifier);
}
/** Simply returns the value of {@link #value}. */
public double getStrength() { return value; }
/**
* Return the feature that should be used to index this feature into a
* lexicon. Specifically, we return this feature with a value of 0 so that
* the same features with different real values will map to the same
* object.
*
* @param lexicon The lexicon into which this feature will be indexed.
* @param training Whether or not the learner is currently training.
* @param label The label of the example containing this feature, or -1
* if we aren't doing per class feature counting.
* @return A feature object appropriate for use as the key of a map.
**/
public Feature getFeatureKey(Lexicon lexicon, boolean training, int label) {
return
new RealPrimitiveStringFeature(containingPackage, generatingClassifier,
identifier, 0);
}
/**
* Returns a new feature object, the same as this one in all respects
* except the {@link #value} field has been multiplied by the specified
* number.
*
* @param m The multiplier.
* @return A new real feature whose value is the product of this feature's
* value and the specified multiplier.
**/
public RealFeature multiply(double m) {
return
new RealPrimitiveStringFeature(containingPackage, generatingClassifier,
identifier, value * m);
}
/**
* Returns a new feature object that's identical to this feature except its
* strength is given by <code>s</code>.
*
* @param s The strength of the new feature.
* @return A new feature object as above, or <code>null</code> if this
* feature cannot take the specified strength.
**/
public Feature withStrength(double s) {
return
new RealPrimitiveStringFeature(containingPackage, generatingClassifier,
identifier, s);
}
/**
* Returns a feature object in which any strings that are being used to
* represent an identifier or value have been encoded in byte strings.
*
* @param e The encoding to use.
* @return A feature object as above; possible this object.
**/
public Feature encode(String e) {
if (e == null || e == "String") return this;
ByteString id =
identifier.length() == 0 ? ByteString.emptyString
: new ByteString(identifier, e);
return
new RealPrimitiveFeature(containingPackage, generatingClassifier, id,
value);
}
/**
* The hash code of a <code>RealPrimitiveStringFeature</code> is the sum of the
* hash codes of the containing package, the identifier, and the value.
*
* @return The hash code for this feature.
**/
public int hashCode() {
return 31 * super.hashCode() + 17 * identifier.hashCode()
+ new Double(value).hashCode();
}
/**
* Two <code>RealPrimitiveStringFeature</code>s are equivalent when their
* containing packages and identifiers are equivalent and their values are
* equal.
*
* @param o The object with which to compare this feature.
* @return <code>true</code> iff the parameter is an equivalent feature.
**/
public boolean equals(Object o) {
if (!super.equals(o)) return false;
if (o instanceof RealPrimitiveStringFeature) {
RealPrimitiveStringFeature f = (RealPrimitiveStringFeature) o;
return identifier.equals(f.identifier) && value == f.value;
}
RealPrimitiveFeature f = (RealPrimitiveFeature) o;
return f.identifier.equals(identifier) && value == f.value;
}
/**
* Some features are functionally equivalent, differing only in the
* encoding of their values; this method will return <code>true</code> iff
* the class of this feature and <code>f</code> are different, but they
* differ only because they encode their values differently. This method
* does not compare the values themselves, however.
*
* @param f Another feature.
* @return See above.
**/
public boolean classEquivalent(Feature f) {
return f instanceof RealPrimitiveFeature;
}
/**
* Used to sort features into an order that is convenient both to page
* through and for the lexicon to read off disk.
*
* @param o An object to compare with.
* @return Integers appropriate for sorting features first by package, then
* by identifier, then by value.
**/
public int compareTo(Object o) {
int d = compareNameStrings(o);
if (d != 0) return d;
RealPrimitiveStringFeature f = (RealPrimitiveStringFeature) o;
d = identifier.compareTo(f.identifier);
if (d != 0) return d;
double difference = value - f.value;
if (difference < 0) return -1;
if (difference > 0) return 1;
return 0;
}
/**
* Writes a string representation of this <code>Feature</code> to the
* specified buffer.
*
* @param buffer The buffer to write to.
**/
public void write(StringBuffer buffer) {
writeNameString(buffer);
buffer.append("(");
buffer.append(value);
buffer.append(")");
}
/**
* Writes a string representation of this <code>Feature</code>'s package,
* generating classifier, and identifier information to the specified
* buffer.
*
* @param buffer The buffer to write to.
**/
public void writeNameString(StringBuffer buffer) {
super.writeNameString(buffer);
buffer.append(":");
buffer.append(identifier);
}
/**
* Writes a complete binary representation of the feature.
*
* @param out The output stream.
**/
public void write(ExceptionlessOutputStream out) {
super.write(out);
out.writeString(identifier);
out.writeDouble(value);
}
/**
* Reads the representation of a feaeture with this object's run-time type
* from the given stream, overwriting the data in this object.
*
* @param in The input stream.
**/
public void read(ExceptionlessInputStream in) {
super.read(in);
identifier = in.readString();
value = in.readDouble();
}
/**
* Writes a binary representation of the feature intended for use by a
* lexicon, omitting redundant information when possible.
*
* @param out The output stream.
* @param lex The lexicon out of which this feature is being written.
* @param c The fully qualified name of the assumed class. The runtime
* class of this feature won't be written if it's equivalent to
* <code>c</code>.
* @param p The assumed package string. This feature's package string
* won't be written if it's equivalent to <code>p</code>.
* @param g The assumed classifier name string. This feature's
* classifier name string won't be written if it's equivalent
* to <code>g</code>.
* @param si The assumed identifier as a string. If this feature has a
* string identifier, it won't be written if it's equivalent to
* <code>si</code>.
* @param bi The assumed identifier as a byte string. If this feature
* has a byte string identifier, it won't be written if it's
* equivalent to <code>bi</code>.
* @return The name of the runtime type of this feature.
**/
public String lexWrite(ExceptionlessOutputStream out, Lexicon lex, String c,
String p, String g, String si, ByteString bi) {
String result = super.lexWrite(out, lex, c, p, g, si, bi);
out.writeString(identifier.equals(si) ? null : identifier);
// NOTE: The lexicon has no use for a real-valued feature's value.
return result;
}
/**
* Reads the representation of a feature with this object's run-time type
* as stored by a lexicon, overwriting the data in this object.
*
* <p> This method is appropriate for reading features as written by
* {@link #lexWrite(ExceptionlessOutputStream,Lexicon,String,String,String,String,ByteString)}.
*
* @param in The input stream.
* @param lex The lexicon we are reading in to.
* @param p The assumed package string. If no package name is given in
* the input stream, the instantiated feature is given this
* package.
* @param g The assumed classifier name string. If no classifier name
* is given in the input stream, the instantiated feature is
* given this classifier name.
* @param si The assumed identifier as a string. If the feature being
* read has a string identifier field and no identifier is
* given in the input stream, the feature is given this
* identifier.
* @param bi The assumed identifier as a byte string. If the feature
* being read has a byte string identifier field and no
* identifier is given in the input stream, the feature is
* given this identifier.
**/
public void lexRead(ExceptionlessInputStream in, Lexicon lex, String p,
String g, String si, ByteString bi) {
super.lexRead(in, lex, p, g, si, bi);
identifier = in.readString();
if (identifier == null) identifier = si;
value = 0;
}
}