Package net.sf.saxon.sort
Class NumericComparer
- java.lang.Object
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- net.sf.saxon.sort.NumericComparer
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- All Implemented Interfaces:
java.io.Serializable
,AtomicComparer
public class NumericComparer extends java.lang.Object implements AtomicComparer, java.io.Serializable
A Comparer used for comparing sort keys when data-type="number". The items to be compared are converted to numbers, and the numbers are then compared directly. NaN values compare equal to each other, and equal to an empty sequence, but less than anything else. This class is used in XSLT only, so there is no need to handle XQuery's "empty least" vs "empty greatest" options.- Author:
- Michael H. Kay
- See Also:
- Serialized Form
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description int
compareAtomicValues(AtomicValue a, AtomicValue b)
Compare two Items by converting them to numbers and comparing the numeric values.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 NumericComparer
getInstance()
AtomicComparer
provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison
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Method Detail
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getInstance
public static NumericComparer getInstance()
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provideContext
public AtomicComparer provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison- Specified by:
provideContext
in interfaceAtomicComparer
- 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
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compareAtomicValues
public int compareAtomicValues(AtomicValue a, AtomicValue b)
Compare two Items by converting them to numbers and comparing the numeric values. If either value cannot be converted to a number, it is treated as NaN, and compares less that the other (two NaN values compare equal).- Specified by:
compareAtomicValues
in interfaceAtomicComparer
- Parameters:
a
- the first Item to be compared.b
- the second Item to be compared.- Returns:
- <0 if a0 if a>b
- Throws:
java.lang.ClassCastException
- if the objects are not Items
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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 interfaceAtomicComparer
- 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
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getComparisonKey
public ComparisonKey getComparisonKey(AtomicValue a)
Get a comparison key for an object. This must satisfy the rule that if two objects are equal according to the XPath eq operator, then their comparison keys are equal according to 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 interfaceAtomicComparer
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