net.sf.saxon.functions
Class Key

java.lang.Object
  extended bynet.sf.saxon.expr.ComputedExpression
      extended bynet.sf.saxon.expr.FunctionCall
          extended bynet.sf.saxon.functions.SystemFunction
              extended bynet.sf.saxon.functions.Key
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, MappingFunction, java.io.Serializable, javax.xml.transform.SourceLocator, XSLTFunction

public class Key
extends SystemFunction
implements MappingFunction, XSLTFunction

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
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
Key()
           
 
Method Summary
 void checkArguments(StaticContext env)
          Method called during static type checking
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 SequenceIterator iterate(XPathContext context)
          Enumerate the results of the expression
 java.lang.Object map(Item item, XPathContext context, java.lang.Object info)
          Implement the MappingFunction interface
 Expression preEvaluate(StaticContext env)
          preEvaluate: this method suppresses compile-time evaluation by doing nothing
 Expression simplify(StaticContext env)
          Simplify: add a third implicit argument, the context document
 
Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, computeCardinality, display, getDetails, getItemType, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault
 
Methods inherited from class net.sf.saxon.expr.FunctionCall
analyze, checkArgumentCount, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, promote, setArguments, setFunctionNameCode, simplifyArguments
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Key

public Key()
Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify: add a third implicit argument, the context document

Specified by:
simplify in interface Expression
Overrides:
simplify in class FunctionCall
Throws:
XPathException

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException
Description copied from class: SystemFunction
Method called during static type checking

Overrides:
checkArguments in class SystemFunction
Throws:
XPathException

computeSpecialProperties

public int computeSpecialProperties()
Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if a property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:
computeSpecialProperties in class SystemFunction

preEvaluate

public Expression preEvaluate(StaticContext env)
preEvaluate: this method suppresses compile-time evaluation by doing nothing

Overrides:
preEvaluate in class FunctionCall

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Enumerate the results of the expression

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 java.lang.Object map(Item item,
                            XPathContext context,
                            java.lang.Object info)
                     throws XPathException
Implement the MappingFunction interface

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