Package net.sf.saxon.expr
Class CastExpression
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.UnaryExpression
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- net.sf.saxon.expr.CastExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,InstructionInfo
,org.xml.sax.Locator
public final class CastExpression extends UnaryExpression
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:
- Serialized Form
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Field Summary
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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.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description CastExpression(Expression source, AtomicType target, boolean allowEmpty)
Create a cast expression
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
allowsEmpty()
Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)static AtomicValue
castStringToQName(java.lang.CharSequence operand, AtomicType targetType, StaticContext env)
Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value.int
computeCardinality()
Get the static cardinality of the expressionint
computeSpecialProperties()
Determine the special properties of this expressionExpression
copy()
Copy an expression.boolean
equals(java.lang.Object other)
Is this expression the same as another expression?Item
evaluateItem(XPathContext context)
Evaluate the expressionvoid
explain(ExpressionPresenter out)
Diagnostic print of expression structure.ItemType
getItemType(TypeHierarchy th)
Get the static type of the expressionAtomicType
getTargetPrimitiveType()
Get the primitive base type of the target type of the castAtomicType
getTargetType()
Get 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 typeExpression
simplify(ExpressionVisitor visitor)
Simplify the expressionboolean
targetIsDerived()
Ask whether the target type is a derived type (not a primitive type)java.lang.String
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.Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
displayExpressionName, displayOperator, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression
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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 Detail
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CastExpression
public CastExpression(Expression source, AtomicType target, boolean allowEmpty)
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 Detail
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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
public AtomicType 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
public AtomicType 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
public Expression simplify(ExpressionVisitor visitor) throws XPathException
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
public ItemType getItemType(TypeHierarchy th)
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
public Expression 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
public Item evaluateItem(XPathContext context) throws XPathException
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
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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toString
public java.lang.String 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
public void explain(ExpressionPresenter out)
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(java.lang.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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