Package net.sf.saxon.expr.sort

Class AtomicSortComparer

  • All Implemented Interfaces:
    AtomicComparer
    public class AtomicSortComparer
extends java.lang.Object
implements AtomicComparer
    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.

    • Field Detail

    • Method Detail

      • 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)
        Parameters:
        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 SimpleCollation so that it can be cloned at run-time.
        itemType - the primitive item type of the values to be compared
        context - Dynamic context (may be an EarlyEvaluationContext)
        Returns:
        a suitable AtomicComparer

      • 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

      • getStringCollator

        public StringCollator getStringCollator()
        Get the underlying StringCollator
        Returns:
        the underlying collator

      • getItemType

        public int getItemType()
        Get the requested item type
        Returns:
        the item type

      • 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.
        Specified by:
        compareAtomicValues in interface AtomicComparer
        Parameters:
        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.
        Returns:
        <0 if a<b, 0 if a=b, >0 if a>b
        Throws:
        java.lang.ClassCastException - if the objects are not comparable
        NoDynamicContextException - if this comparer required access to dynamic context information, notably the implicit timezone, and this information is not available. In general this happens if a context-dependent comparison is attempted at compile-time, and it signals the compiler to generate code that tries again at run-time.

      • compareNonComparables

        protected int compareNonComparables​(AtomicValue a,
                                    AtomicValue b)
        Compare two values that are known to be non-comparable. In the base class this method throws a ClassCastException. In a subclass it is overridden to return SequenceTool.INDETERMINATE_ORDERING
        Parameters:
        a - the first value to be compared
        b - the second value to be compared
        Returns:
        the result of the comparison
        Throws:
        java.lang.ClassCastException - if the two values are not comparable

      • 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.
        Specified by:
        comparesEqual 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 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.
        Returns:
        true if the values are equal, false if not
        Throws:
        java.lang.ClassCastException - if the objects are not comparable
        NoDynamicContextException

      • 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