net.sf.saxon.sort

Class DoubleSortComparer

public class DoubleSortComparer extends 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
intcompareAtomicValues(AtomicValue a, AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type.
booleancomparesEqual(AtomicValue a, AtomicValue b)
Test whether two values compare equal.
ComparisonKeygetComparisonKey(AtomicValue a)
Get a comparison key for an object.
static DoubleSortComparergetInstance()
Get the singular instance of this class
AtomicComparerprovideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison

Method Detail

compareAtomicValues

public int compareAtomicValues(AtomicValue a, AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type.

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

Throws: ClassCastException if the objects are not comparable

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

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.

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

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