net.sf.saxon.functions
Class DistinctValues

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.FunctionCall
          extended by net.sf.saxon.functions.SystemFunction
              extended by net.sf.saxon.functions.CollatingFunction
                  extended by net.sf.saxon.functions.DistinctValues
All Implemented Interfaces:
Serializable, Expression, MappingFunction

public class DistinctValues
extends CollatingFunction
implements MappingFunction

The XPath 2.0 distinct-values() function

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.functions.SystemFunction
operation
 
Fields inherited from class net.sf.saxon.expr.FunctionCall
argument
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
DistinctValues()
           
 
Method Summary
protected  AtomicSortComparer getAtomicSortComparer(int arg, XPathContext context)
          Get a AtomicSortComparer that can be used to compare values
 SequenceIterator iterate(XPathContext context)
          Evaluate the function to return an iteration of selected values or nodes.
 Object map(Item item, XPathContext context, Object info)
          Mapping function.
 
Methods inherited from class net.sf.saxon.functions.CollatingFunction
getAtomicComparer, getCollator, preEvaluate
 
Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, checkArguments, computeCardinality, display, getDetails, getItemType, getName, getRequiredType, main, makeSystemFunction, useContextItemAsDefault
 
Methods inherited from class net.sf.saxon.expr.FunctionCall
analyze, checkArgumentCount, getNumberOfArguments, getSubExpressions, promote, setArguments, simplify, simplifyArguments
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSpecialProperties, markTailFunctionCalls, setLineNumber, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DistinctValues

public DistinctValues()
Method Detail

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Evaluate the function to return an iteration of selected values or nodes.

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
context - supplies the context for evaluation
Returns:
a SequenceIterator that can be used to iterate over the result of the expression
Throws:
XPathException - if any dynamic error occurs evaluating the expression

map

public Object map(Item item,
                  XPathContext context,
                  Object info)
           throws XPathException
Mapping function. Maps a duplicate item to null (no item in the result) and any other item to itself. The general-purpose "info" object is in this case a pair of two objects, the HashSet used for the value lookup, and the AtomicComparer used to compare values.

Specified by:
map in interface MappingFunction
Parameters:
item - The item to be mapped. If context is supplied, this must be the same as context.currentItem().
context - The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.
info - Arbitrary information supplied by the creator of the MappingIterator. It must be read-only and immutable for the duration of the iteration.
Returns:
either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.
Throws:
XPathException

getAtomicSortComparer

protected AtomicSortComparer getAtomicSortComparer(int arg,
                                                   XPathContext context)
                                            throws XPathException
Get a AtomicSortComparer that can be used to compare values

Parameters:
arg - the position of the argument (starting at 0) containing the collation name. If this argument was not supplied, the default collation is used
context - The dynamic evaluation context.
Throws:
XPathException