net.sf.saxon.sort

Class DoubleSortComparer

Implemented Interfaces:
AtomicComparer, Serializable

public class DoubleSortComparer
extends java.lang.Object
implements AtomicComparer

An AtomicComparer used for sorting values that are known to be numeric. It also supports a separate method for getting a collation key to test equality of items. This comparator treats NaN values as equal to each other, and less than any other value.
Author:
Michael H. Kay

Method Summary

int
compareAtomicValues(AtomicValue a, AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type.
boolean
comparesEqual(AtomicValue a, AtomicValue b)
Test whether two values compare equal.
ComparisonKey
getComparisonKey(AtomicValue a)
Get a comparison key for an object.
static DoubleSortComparer
getInstance()
Get the singular instance of this class
AtomicComparer
provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison

Method Details

compareAtomicValues

public int compareAtomicValues(AtomicValue a,
                               AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type.
Specified by:
compareAtomicValues in interface AtomicComparer
Parameters:
a - the first object to be compared. It is intended that this should normally be an instance of AtomicValue, though this restriction is not enforced. If it is a StringValue, the collator is used to compare the values, otherwise the value must implement the java.util.Comparable interface.
b - the second object to be compared. This must be comparable with the first object: for example, if one is a string, they must both be strings.
Returns:
<0 if a0 if a>b

comparesEqual

public boolean comparesEqual(AtomicValue a,
                             AtomicValue b)
Test whether two values compare equal. Note that for this comparer, NaN is considered equal to itself
Specified by:
comparesEqual in interface AtomicComparer

getComparisonKey

public ComparisonKey getComparisonKey(AtomicValue a)
Get a comparison key for an object. This must satisfy the rule that if two objects are equal as defined by the XPath eq operator, then their comparison keys are equal as defined by the Java equals() method, and vice versa. There is no requirement that the comparison keys should reflect the ordering of the underlying objects.
Specified by:
getComparisonKey in interface AtomicComparer

getInstance

public static DoubleSortComparer getInstance()
Get the singular instance of this class
Returns:
the singular instance

provideContext

public AtomicComparer provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison
Specified by:
provideContext in interface AtomicComparer
Parameters:
context - the dynamic evaluation context
Returns:
either the original AtomicComparer, or a new AtomicComparer in which the context is known. The original AtomicComparer is not modified