net.sf.saxon.functions
Class Trace

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.FunctionCall
          extended by net.sf.saxon.functions.SystemFunction
              extended by net.sf.saxon.functions.Trace
All Implemented Interfaces:
Serializable, SourceLocator, EvaluableItem, SequenceIterable, InstructionInfoProvider

public class Trace
extends SystemFunction

This class supports the XPath 2.0 function trace(). The value is traced to the System.err stream, unless a TraceListener is in use, in which case the information is sent to the TraceListener

See Also:
Serialized Form

Nested Class Summary
 class Trace.TracingIterator
          Tracing Iterator class
 
Field Summary
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
Trace()
           
 
Method Summary
 int computeCardinality()
          Get the static cardinality
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 Item evaluateItem(XPathContext context)
          Evaluate the function
 SequenceIterator iterate(XPathContext context)
          Iterate over the results of the function
 Expression preEvaluate(ExpressionVisitor visitor)
          preEvaluate: this method suppresses compile-time evaluation by doing nothing
 Expression simplify(ExpressionVisitor visitor)
          Simplify the function call.
 
Methods inherited from class net.sf.saxon.functions.SystemFunction
addDocToPathMap, checkArguments, copy, getDetails, getErrorCodeForTypeErrors, getItemType, makeSystemFunction, optimize, setDetails
 
Methods inherited from class net.sf.saxon.expr.FunctionCall
addExternalFunctionCallToPathMap, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, promote, replaceSubExpression, setArguments, setFunctionName, toString, typeCheck
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, effectiveBooleanValue, evaluateAsString, explain, findParentOf, getCardinality, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterateEvents, markTailFunctionCalls, process, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Trace

public Trace()
Method Detail

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
Simplify the function call. This implementation saves the static namespace context, in case it is needed by the TraceListener.

Overrides:
simplify in class FunctionCall
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

preEvaluate

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

Overrides:
preEvaluate in class FunctionCall
Parameters:
visitor - an expression visitor
Returns:
the result of the early evaluation, or the original expression, or potentially a simplified expression

computeSpecialProperties

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

Overrides:
computeSpecialProperties in class SystemFunction
Returns:
the special properties, as a bit-significant integer

computeCardinality

public int computeCardinality()
Get the static cardinality

Overrides:
computeCardinality in class SystemFunction
Returns:
the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate the function

Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in class Expression
Parameters:
context - The context in which the expression is to be evaluated
Returns:
the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
Throws:
XPathException - if any dynamic error occurs evaluating the expression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Iterate over the results of the function

Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in class Expression
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


Copyright (C) Michael H. Kay. All rights reserved.