Package net.sf.saxon.expr
Class CastableExpression
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.CastingExpression
net.sf.saxon.expr.CastableExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,InstructionInfo
,Locator
Castable Expression: implements "Expr castable as atomic-type?".
The implementation simply wraps a cast expression with a try/catch.
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.CastingExpression
converter, nsResolver
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
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Constructor Summary
ConstructorsConstructorDescriptionCastableExpression
(Expression source, AtomicType target, boolean allowEmpty) Create a "castable" expression of the form "source castable as target" -
Method Summary
Modifier and TypeMethodDescriptionint
Determine the static cardinality.copy()
Copy an expression.boolean
effectiveBooleanValue
(XPathContext context) Get the effective boolean value of the expression.boolean
Is this expression the same as another expression?evaluateItem
(XPathContext context) Evaluate the expressionvoid
Diagnostic print of expression structure.Determine the data type of the result of the Castable expressionint
hashCode()
get HashCode for comparing two expressions.optimize
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Optimize the expressionprotected Expression
toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.typeCheck
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.CastingExpression
allowsEmpty, computeSpecialProperties, getConverter, getNamespaceResolver, getTargetPrimitiveType, getTargetType, isOperandIsStringLiteral, setAllowEmpty, setNamespaceResolver, setOperandIsStringLiteral, setTargetType, simplify
Methods inherited from class net.sf.saxon.expr.UnaryExpression
displayOperator, getBaseExpression, iterateSubExpressions, promote, replaceSubExpression
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Details
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CastableExpression
Create a "castable" expression of the form "source castable as target"- Parameters:
source
- The source expressiontarget
- The type being tested againstallowEmpty
- true if an empty sequence is acceptable, that is if the expression was written as "source castable as target?"
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Method Details
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Type-check the expression- Overrides:
typeCheck
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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:
XPathException
- if an error is discovered during this phase (typically a type error)
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preEvaluate
- Throws:
XPathException
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optimize
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Optimize the expression- Overrides:
optimize
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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:
XPathException
- if an error is discovered during this phase (typically a type error)
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equals
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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hashCode
public int hashCode()get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.- Overrides:
hashCode
in classUnaryExpression
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getItemType
Determine the data type of the result of the Castable expression- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
- the type hierarchy cache- 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
- Returns:
- the computed cardinality, as one of the values
StaticProperty.ALLOWS_ZERO_OR_ONE
,StaticProperty.EXACTLY_ONE
,StaticProperty.ALLOWS_ONE_OR_MORE
,StaticProperty.ALLOWS_ZERO_OR_MORE
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copy
Description copied from class:Expression
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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evaluateItem
Evaluate the expression- Overrides:
evaluateItem
in classExpression
- 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
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effectiveBooleanValue
Description copied from class:Expression
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.- Overrides:
effectiveBooleanValue
in classExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the effective boolean value
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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toString
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax- Overrides:
toString
in classUnaryExpression
- Returns:
- a representation of the expression as a string
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explain
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Overrides:
explain
in classUnaryExpression
- Parameters:
out
- the expression presenter used to display the structure
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