net.sf.saxon.sort

Class EqualityComparer

Implemented Interfaces:
AtomicComparer, Serializable

public class EqualityComparer
extends java.lang.Object
implements AtomicComparer

A comparer for comparing two atomic values where (a) equals is defined, and is implemented using the Java equals() method, and (b) ordering is not defined, and results in a dynamic error.

Field Summary

static EqualityComparer
THE_INSTANCE

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)
Compare two AtomicValue objects for equality according to the rules for their data type.
ComparisonKey
getComparisonKey(AtomicValue a)
Get a comparison key for an object.
static EqualityComparer
getInstance()
Get the singleton instance of this class
AtomicComparer
provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison

Field Details

THE_INSTANCE

public static EqualityComparer THE_INSTANCE

Method Details

compareAtomicValues

public int compareAtomicValues(AtomicValue a,
                               AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type. UntypedAtomic values are compared as if they were strings; if different semantics are wanted, the conversion must be done by the caller.
Specified by:
compareAtomicValues in interface AtomicComparer
Parameters:
a - the first object to be compared. It is intended that this should 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)
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.
Specified by:
comparesEqual in interface AtomicComparer
Parameters:
a - the first object to be compared. This must be an AtomicValue and it must implement equals() with context-free XPath comparison semantics
b - the second object to be compared. This must be an AtomicValue and it must implement equals() with context-free XPath comparison semantics
Returns:
true if the values are equal, false if not

getComparisonKey

public ComparisonKey getComparisonKey(AtomicValue a)
Get a comparison key for an object. This must satisfy the rule that if two objects are equal, then their comparison keys are equal, 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 EqualityComparer getInstance()
Get the singleton instance of this class
Returns:
the singleton instance of this class

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