net.sf.saxon.expr
Class ErrorExpression

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.ErrorExpression

All Implemented Interfaces:

Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public class ErrorExpression

extends ComputedExpression

Error expression: this expression is generated when the supplied expression cannot be parsed, and the containing element enables forwards-compatible processing. It defers the generation of an error message until an attempt is made to evaluate the expression

See Also:

Serialized Form

Field Summary

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

ErrorExpression(XPathException exception)
Constructor

Method Summary

int	computeCardinality() Determine the static cardinality
void	display(int level, NamePool pool, java.io.PrintStream out) Diagnostic print of expression structure
Item	evaluateItem(XPathContext context) Evaluate the expression.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the expression, if possible
SequenceIterator	iterate(XPathContext context) Iterate over the expression.
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression.

Methods inherited from class net.sf.saxon.expr.ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterateSubExpressions, markTailFunctionCalls, process, promote, resetStaticProperties, setLocationId, setParentExpression, simplify, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

ErrorExpression

public ErrorExpression(XPathException exception)

Constructor

Parameters:

exception - the error found when parsing this expression

Method Detail

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression.

Parameters:

env - the static context of the expression

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException

optimize

public Expression optimize(Optimizer opt,
                           StaticContext env,
                           ItemType contextItemType)
                    throws XPathException

Description copied from interface: Expression

Perform optimisation of an expression and its subexpressions.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Parameters:

opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.

env - the static context of the expression

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression. This always throws the exception registered when the expression was first parsed.

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 expression. This always throws the exception registered when the expression was first parsed.

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression, if possible

Parameters:

th -

Returns:

Type.ITEM (meaning not known in advance)

computeCardinality

public int computeCardinality()

Determine the static cardinality

Specified by:

computeCardinality in class ComputedExpression

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)

Diagnostic print of expression structure

Parameters:

level - indentation level for this expression

pool - NamePool used to expand any names appearing in the expression

out - Output destination