net.sf.saxon.expr

Class CastableExpression

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.CastableExpression

All Implemented Interfaces:

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

public final class CastableExpression
extends UnaryExpression

Castable Expression: implements "Expr castable as atomic-type?". The implementation simply wraps a cast expression with a try/catch.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
(package private) boolean	allowEmpty
(package private) AtomicType	targetType

Fields inherited from class net.sf.saxon.expr.UnaryExpression

operand

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

Constructors

Constructor and Description
CastableExpression(Expression source, AtomicType target, boolean allowEmpty)

Method Summary

Modifier and Type	Method and Description
int	computeCardinality() Determine the static cardinality.
int	computeSpecialProperties() Determine the special properties of this expression
protected java.lang.String	displayOperator(Configuration config) Give a string representation of the operator for use in diagnostics
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value of the expression.
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
Item	evaluateItem(XPathContext context) Evaluate the expression
ItemType	getItemType(TypeHierarchy th) Determine the data type of the result of the Castable expression
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType) Optimize the expression
Expression	simplify(StaticContext env) Simplify the expression
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

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

display, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression

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

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

Methods inherited from class java.lang.Object

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

Field Detail

targetType

AtomicType targetType

allowEmpty

boolean allowEmpty

Constructor Detail

CastableExpression

public CastableExpression(Expression source,
                          AtomicType target,
                          boolean allowEmpty)

Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify the expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class UnaryExpression

Parameters:

env - the static context

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

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

Type-check the expression

Specified by:

typeCheck in interface Expression

Overrides:

typeCheck in class UnaryExpression

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:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

optimize

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

Optimize the expression

Specified by:

optimize in interface Expression

Overrides:

optimize in class UnaryExpression

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:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the result of the Castable expression

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

computeCardinality

public int computeCardinality()

Description copied from class: UnaryExpression

Determine the static cardinality. Default implementation returns the cardinality of the operand

Overrides:

computeCardinality in class UnaryExpression

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NON_CREATIVE.

evaluateItem

public Item evaluateItem(XPathContext context)

Evaluate the expression

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

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)

Description copied from class: ComputedExpression

Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class ComputedExpression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the effective boolean value

displayOperator

protected java.lang.String displayOperator(Configuration config)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Parameters:

config -

Returns:

the operator, as a string