net.sf.saxon.functions
Class Trace

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.FunctionCall
              |
              +--net.sf.saxon.functions.SystemFunction
                    |
                    +--net.sf.saxon.functions.Trace

All Implemented Interfaces:

Expression, java.io.Serializable

public class Trace

extends SystemFunction

This class supports the XPath 2.0 function trace(). At present the value is simply traced to the System.err stream

See Also:

Serialized Form

Nested Class Summary
class	Trace.TracingIterator           Tracing Iterator class

 

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

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

 

Methods inherited from class net.sf.saxon.functions.SystemFunction

addContextDocumentArgument, checkArguments, 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, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSourceLocator, getSpecialProperties, markTailFunctionCalls, setLineNumber, typeError

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Constructor Detail

Trace

public Trace()

preEvaluate

public Expression preEvaluate(StaticContext env)

preEvaluate: this method suppresses compile-time evaluation by doing nothing

Overrides:

preEvaluate in class FunctionCall

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 ComputedExpression

computeCardinality

public int computeCardinality()

Get the static cardinality

Overrides:

computeCardinality in class SystemFunction

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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 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