Package net.sf.saxon.expr
Class CastExpression
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.CastExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,InstructionInfo
,Locator
Cast Expression: implements "cast as data-type ( expression )". It also allows an internal
cast, which has the same semantics as a user-requested cast, but maps an empty sequence to
an empty sequence.
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
ConstructorsConstructorDescriptionCastExpression
(Expression source, AtomicType target, boolean allowEmpty) Create a cast expression -
Method Summary
Modifier and TypeMethodDescriptionboolean
Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)static AtomicValue
castStringToQName
(CharSequence operand, AtomicType targetType, StaticContext env) Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value.int
Get the static cardinality of the expressionint
Determine the special properties of this expressioncopy()
Copy an expression.boolean
Is this expression the same as another expression?evaluateItem
(XPathContext context) Evaluate the expressionvoid
Diagnostic print of expression structure.Get the static type of the expressionGet the primitive base type of the target type of the castGet the target type (the result type)static boolean
isPossibleCast
(int source, int target) Determine whether casting from a source type to a target type is possibleboolean
isUpCast()
Ask whether this is a cast to a supertype of the original typesimplify
(ExpressionVisitor visitor) Simplify the expressionboolean
Ask whether the target type is a derived type (not a primitive type)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, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.UnaryExpression
displayExpressionName, displayOperator, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterate, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Details
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CastExpression
Create a cast expression- Parameters:
source
- expression giving the value to be convertedtarget
- the type to which the value is to be convertedallowEmpty
- true if the expression allows an empty sequence as input, producing an empty sequence as output. If false, an empty sequence is a type error.
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Method Details
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isPossibleCast
public static boolean isPossibleCast(int source, int target) Determine whether casting from a source type to a target type is possible- Parameters:
source
- a primitive type (one that has an entry in the casting table)target
- another primitive type- Returns:
- true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)
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getTargetPrimitiveType
Get the primitive base type of the target type of the cast- Returns:
- the primitive type of the target type
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getTargetType
Get the target type (the result type)- Returns:
- the target type
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allowsEmpty
public boolean allowsEmpty()Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)- Returns:
- true if an empty sequence is accepted
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targetIsDerived
public boolean targetIsDerived()Ask whether the target type is a derived type (not a primitive type)- Returns:
- true if the target type is a derived type
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isUpCast
public boolean isUpCast()Ask whether this is a cast to a supertype of the original type- Returns:
- true if this is an upcast. This means the value stays unchanged and only the type label changes
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simplify
Simplify the expression- Overrides:
simplify
in classUnaryExpression
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType 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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computeCardinality
public int computeCardinality()Get the static cardinality of the expression- 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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getItemType
Get the static type of the 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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computeSpecialProperties
public int computeSpecialProperties()Determine the special properties of this expression- Overrides:
computeSpecialProperties
in classUnaryExpression
- Returns:
StaticProperty.NON_CREATIVE
.
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copy
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- Specified by:
evaluateItem
in interfaceEvaluableItem
- 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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equals
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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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
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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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castStringToQName
public static AtomicValue castStringToQName(CharSequence operand, AtomicType targetType, StaticContext env) throws XPathException Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time- Parameters:
operand
- the value to be convertedtargetType
- the type to which it is to be convertedenv
- the static context- Returns:
- the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a derived AtomicValue derived from QName or NOTATION
- Throws:
XPathException
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