Package net.sf.saxon.expr.sort

Class NumericComparer

  • All Implemented Interfaces:
    java.io.Serializable, AtomicComparer
    Direct Known Subclasses:
    NumericComparer11
    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

    • Constructor Detail

      • NumericComparer

        protected NumericComparer()

    • Method Detail

      • 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:
        <0 if a0 if a>b
        Throws:
        java.lang.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:
        java.lang.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