net.sf.saxon.expr.sort

Class UntypedNumericComparer

java.lang.Object

net.sf.saxon.expr.sort.UntypedNumericComparer

All Implemented Interfaces:

AtomicComparer

public class UntypedNumericComparer
extends java.lang.Object
implements AtomicComparer

A specialist comparer that implements the rules for comparing an untypedAtomic value (always the first operand) to a numeric value (always the second operand)

Constructor Summary

Constructors

Constructor and Description
UntypedNumericComparer()

Method Summary

Modifier and Type	Method and Description
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.
StringCollator	getCollator() Get the collation used by this AtomicComparer if any
AtomicComparer	provideContext(XPathContext context) Supply the dynamic context in case this is needed for the comparison
static boolean	quickCompare(UntypedAtomicValue a0, NumericValue a1, int operator, ConversionRules rules) Optimized routine to compare an untyped atomic value with a numeric value.
java.lang.String	save() Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UntypedNumericComparer

public UntypedNumericComparer()

Method Detail

quickCompare

public static boolean quickCompare(UntypedAtomicValue a0,
                                   NumericValue a1,
                                   int operator,
                                   ConversionRules rules)
                            throws XPathException

Optimized routine to compare an untyped atomic value with a numeric value. This attempts to deliver a quick answer if the comparison is obviously false, without performing the full string-to-double conversion

Parameters:

a0 - the untypedAtomic comparand

a1 - the numeric comparand

operator - the comparison operator: a singleton operator such as Token.FEQ

rules - the conversion rules

Returns:

the result of the comparison

Throws:

XPathException - if the first operand is not convertible to a double

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 a<b, 0 if a=b, >0 if a>b

Throws:

java.lang.ClassCastException - if the objects are not comparable

getCollator

public StringCollator getCollator()

Get the collation used by this AtomicComparer if any

Specified by:

getCollator in interface AtomicComparer

Returns:

the collation used for comparing strings, or null if not applicable

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

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.

b - the second object to be compared.

Returns:

true if the values are equal, false if not

Throws:

java.lang.ClassCastException - if the objects are not comparable

save

public java.lang.String save()

Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Specified by:

save in interface AtomicComparer

Returns:

a string representation of the AtomicComparer