Package net.sf.saxon.expr
Class CastableExpression
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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- net.sf.saxon.expr.UnaryExpression
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- net.sf.saxon.expr.CastableExpression
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- 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
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Field Summary
Fields Modifier and Type Field Description (package private) boolean
allowEmpty
(package private) AtomicType
targetType
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Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
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Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors Constructor Description CastableExpression(Expression source, AtomicType target, boolean allowEmpty)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
computeCardinality()
Determine the static cardinality.int
computeSpecialProperties()
Determine the special properties of this expressionprotected java.lang.String
displayOperator(Configuration config)
Give a string representation of the operator for use in diagnosticsboolean
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 expressionItemType
getItemType(TypeHierarchy th)
Determine the data type of the result of the Castable expressionExpression
optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Optimize the expressionExpression
simplify(StaticContext env)
Simplify the expressionExpression
typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
display, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression
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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
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Field Detail
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targetType
AtomicType targetType
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allowEmpty
boolean allowEmpty
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Constructor Detail
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CastableExpression
public CastableExpression(Expression source, AtomicType target, boolean allowEmpty)
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Method Detail
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simplify
public Expression simplify(StaticContext env) throws XPathException
Simplify the expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classUnaryExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
Type-check the expression- Specified by:
typeCheck
in interfaceExpression
- Overrides:
typeCheck
in classUnaryExpression
- Parameters:
env
- the static context of the expressioncontextItemType
- 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 toType.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
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
Optimize the expression- Specified by:
optimize
in interfaceExpression
- Overrides:
optimize
in classUnaryExpression
- 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 expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
net.sf.saxon.trans.StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the result of the Castable expression- Specified by:
getItemType
in interfaceExpression
- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
-- Returns:
- the item type of the items in the result sequence, insofar as this is known statically.
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computeCardinality
public int computeCardinality()
Description copied from class:UnaryExpression
Determine the static cardinality. Default implementation returns the cardinality of the operand- Overrides:
computeCardinality
in classUnaryExpression
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computeSpecialProperties
public int computeSpecialProperties()
Determine the special properties of this expression- Overrides:
computeSpecialProperties
in classUnaryExpression
- Returns:
StaticProperty.NON_CREATIVE
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evaluateItem
public Item evaluateItem(XPathContext context)
Evaluate the expression- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classComputedExpression
- 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
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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 interfaceExpression
- Overrides:
effectiveBooleanValue
in classComputedExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the effective boolean value
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displayOperator
protected java.lang.String displayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics- Specified by:
displayOperator
in classUnaryExpression
- Parameters:
config
-- Returns:
- the operator, as a string
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