net.sf.saxon.sort
Class AtomicSortComparer
java.lang.Object
net.sf.saxon.sort.AtomicSortComparer
- AtomicComparer, Serializable
public class AtomicSortComparer
extends java.lang.Object
An AtomicComparer used for comparing atomic values of arbitrary item types. It encapsulates
a collator that is used when the values to be compared are strings. It also supports
a separate method for testing equality of items, which can be used for data types that
are not ordered.
The AtomicSortComparer is identical to the GenericAtomicComparer except for its handling
of NaN: it treats NaN values as lower than any other value, and as equal to each other.
compareAtomicValues
public int compareAtomicValues(AtomicValue a,
AtomicValue b)
throws NoDynamicContextException
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.
- compareAtomicValues in interface AtomicComparer
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.
comparesEqual
public boolean comparesEqual(AtomicValue a,
AtomicValue b)
throws NoDynamicContextException
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.
- comparesEqual in interface AtomicComparer
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 equals() method.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.
- true if the values are equal, false if not
getComparisonKey
public ComparisonKey getComparisonKey(AtomicValue a)
throws NoDynamicContextException
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.
- getComparisonKey in interface AtomicComparer
getItemType
public int getItemType()
Get the requested item type
getStringCollator
public StringCollator getStringCollator()
Get the underlying StringCollator
makeSortComparer
public static AtomicComparer makeSortComparer(StringCollator collator,
int itemType,
XPathContext context)
Factory method to get an atomic comparer suitable for sorting or for grouping (operations in which
NaN is considered equal to NaN)
collator
- Collating comparer to be used when comparing strings. This argument may be null
if the itemType excludes the possibility of comparing strings. If the method is called at compile
time, this should be a NamedCollation so that it can be cloned at run-time.itemType
- the primitive item type of the values to be comparedcontext
- Dynamic context (may be an EarlyEvaluationContext)
- a suitable AtomicComparer
provideContext
public AtomicComparer provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison
- provideContext in interface AtomicComparer
context
- the dynamic evaluation context
- either the original AtomicComparer, or a new AtomicComparer in which the context
is known. The original AtomicComparer is not modified