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## net.sf.saxon.functions
Class Error

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.FunctionCall
              net.sf.saxon.functions.SystemFunction
                  net.sf.saxon.functions.Error

All Implemented Interfaces:
  Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

    public class Error

extends SystemFunction

Implement XPath function fn:error()

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.Expression
`EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD`

Constructor Summary
`Error()`

Method Summary
`Item` | `evaluateItem(XPathContext context)` Evaluation of the expression always throws an error
`void` | `evaluatePendingUpdates(XPathContext context, PendingUpdateList pul)` Evaluate an updating expression, adding the results to a Pending Update List.
`boolean` | `isVacuousExpression()` Determine whether this is a vacuous expression as defined in the XQuery update specification
`Expression` | `preEvaluate(ExpressionVisitor visitor)` preEvaluate: this method suppresses compile-time evaluation by doing nothing

Methods inherited from class net.sf.saxon.functions.SystemFunction
`addContextDocumentArgument, addDocToPathMap, checkArguments, computeCardinality, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getImplementationMethod, getItemType, getRequiredType, makeSystemFunction, optimize, setDetails, useContextItemAsDefault`

Methods inherited from class net.sf.saxon.expr.FunctionCall
`addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck`

Methods inherited from class net.sf.saxon.expr.Expression
`addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Constructor Detail

### Error

    public Error()

Method Detail

### 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

### isVacuousExpression

    public boolean isVacuousExpression()

  Determine whether this is a vacuous expression as defined in the XQuery update specification

  Overrides:
    `isVacuousExpression` in class `Expression`
  Returns:
    true if this expression is vacuous

### evaluateItem

    public Item evaluateItem(XPathContext context)
                      throws XPathException

  Evaluation of the expression always throws an error

  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

### evaluatePendingUpdates

    public void evaluatePendingUpdates(XPathContext context,
                                       PendingUpdateList pul)
                                throws XPathException

  Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException

  Overrides:
    `evaluatePendingUpdates` in class `Expression`
  Parameters:
    `context` - the XPath dynamic evaluation context
    `pul` - the pending update list to which the results should be written
  Throws:
    `XPathException`

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Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.