package net.sf.saxon.sort;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.StandardNames;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.DoubleValue;
import net.sf.saxon.value.NumericValue;
import net.sf.saxon.value.Value;
/**
* A Comparer used for comparing sort keys when data-type="number". The items to be
* compared are converted to numbers, and the numbers are then compared directly. NaN values
* compare equal to each other, and equal to an empty sequence, but less than anything else.
* <p/>
* This class is used in XSLT only, so there is no need to handle XQuery's "empty least" vs
* "empty greatest" options.
*
* @author Michael H. Kay
*
*/
public class NumericComparer implements AtomicComparer, java.io.Serializable {
private static NumericComparer THE_INSTANCE = new NumericComparer();
public static NumericComparer getInstance() {
return THE_INSTANCE;
}
private NumericComparer() {
}
/**
* Supply the dynamic context in case this is needed for the comparison
* @param context the dynamic evaluation context
* @return either the original AtomicComparer, or a new AtomicComparer in which the context
* is known. The original AtomicComparer is not modified
*/
public AtomicComparer provideContext(XPathContext context) {
return this;
}
/**
* Compare two Items by converting them to numbers and comparing the numeric values. If either
* value cannot be converted to a number, it is treated as NaN, and compares less that the other
* (two NaN values compare equal).
* @param a the first Item to be compared.
* @param b the second Item to be compared.
* @return <0 if a<b, 0 if a=b, >0 if a>b
* @throws ClassCastException if the objects are not Items
*/
public int compareAtomicValues(AtomicValue a, AtomicValue b) {
double d1, d2;
if (a instanceof NumericValue) {
d1 = ((NumericValue)a).getDoubleValue();
} else if (a == null) {
d1 = Double.NaN;
} else {
try {
d1 = Value.stringToNumber(a.getStringValueCS());
} catch (NumberFormatException err) {
d1 = Double.NaN;
}
}
if (b instanceof NumericValue) {
d2 = ((NumericValue)b).getDoubleValue();
} else if (b == null) {
d2 = Double.NaN;
} else {
try {
d2 = Value.stringToNumber(b.getStringValueCS());
} catch (NumberFormatException err) {
d2 = Double.NaN;
}
}
if (Double.isNaN(d1)) {
if (Double.isNaN(d2)) {
return 0;
} else {
return -1;
}
}
if (Double.isNaN(d2)) {
return +1;
}
if (d1 < d2) return -1;
if (d1 > d2) return +1;
return 0;
}
/**
* Compare two AtomicValue objects for equality according to the rules for their data type. UntypedAtomic
* values are compared by converting to the type of the other operand.
*
* @param a the first object to be compared.
* @param b the second object to be compared.
* @return true if the values are equal, false if not
* @throws ClassCastException if the objects are not comparable
*/
public boolean comparesEqual(AtomicValue a, AtomicValue b) {
return compareAtomicValues(a, b) == 0;
}
/**
* Get a comparison key for an object. This must satisfy the rule that if two objects are equal
* according to the XPath eq operator, then their comparison keys are equal according to the Java
* equals() method, and vice versa. There is no requirement that the
* comparison keys should reflect the ordering of the underlying objects.
*/
public ComparisonKey getComparisonKey(AtomicValue a) {
if (a instanceof NumericValue) {
return new ComparisonKey(StandardNames.XS_NUMERIC, toDoubleValue(((NumericValue)a)));
} else if (a == null) {
return new ComparisonKey(StandardNames.XS_NUMERIC, "NaN");
} else {
try {
double d = Value.stringToNumber(a.getStringValueCS());
return new ComparisonKey(StandardNames.XS_NUMERIC, new DoubleValue(d));
} catch (NumberFormatException err) {
return new ComparisonKey(StandardNames.XS_NUMERIC, "NaN");
}
}
}
private DoubleValue toDoubleValue(NumericValue nv) {
if (nv instanceof DoubleValue) {
return ((DoubleValue)nv);
} else {
return new DoubleValue(nv.getDoubleValue());
}
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of this module is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//