Package net.sf.saxon.expr.sort

Class NumericComparer

java.lang.Object
net.sf.saxon.expr.sort.NumericComparer
All Implemented Interfaces:
Serializable, AtomicComparer
Direct Known Subclasses:
NumericComparer11
public class NumericComparer extends Object implements AtomicComparer, 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:

  • Field Details

  • Constructor Details

    • NumericComparer

      protected NumericComparer()

  • Method Details

    • getInstance

      public static NumericComparer getInstance()

    • getCollator

      public StringCollator getCollator()
      Description copied from interface: AtomicComparer
      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

    • 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 interface AtomicComparer
      Parameters:
      a - the first Item to be compared.
      b - the second Item to be compared.
      Returns:
      invalid input: '<'0 if ainvalid input: '<'b, 0 if a=b, >0 if a>b
      Throws:
      ClassCastException - if the objects are not Items

    • 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:
      ClassCastException - if the objects are not comparable

    • 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 interface AtomicComparer