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:
ExportAgent
,Locatable
,IdentityComparable
,Traceable
Castable Expression: implements "Expr castable as atomic-type?".
The implementation simply wraps a cast expression with a try/catch.
-
Field Summary
Fields inherited from class net.sf.saxon.expr.CastingExpression
converter
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD
-
Constructor Summary
ConstructorsConstructorDescriptionCastableExpression
(Expression source, AtomicType target, boolean allowEmpty) Create a "castable" expression of the form "source castable as target" -
Method Summary
Modifier and TypeMethodDescriptionprotected int
Determine the static cardinality.protected int
get HashCode for comparing two expressions.copy
(RebindingMap rebindings) 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.Make an elaborator for this expressionGet a name identifying the kind of expression, in terms meaningful to a user.int
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Determine the data type of the result of the Castable expressiongetStaticUType
(UType contextItemType) Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.optimize
(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Optimize the expressiontoString()
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, ContextItemStaticInfo contextInfo) Type-check the expressionMethods inherited from class net.sf.saxon.expr.CastingExpression
allowsEmpty, computeSpecialProperties, export, getConverter, getIntrinsicDependencies, getNamespaceResolver, getOperandRole, getTargetPrimitiveType, getTargetType, isOperandIsStringLiteral, setAllowEmpty, setOperandIsStringLiteral, setTargetType, simplify
Methods inherited from class net.sf.saxon.expr.UnaryExpression
displayOperator, emitExtraAttributes, getBaseExpression, getOperand, operands, setBaseExpression, toShortString
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dispatchTailCall, dynamicError, evaluateAsString, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
-
Constructor Details
-
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?"
-
-
Method Details
-
typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException Type-check the expression- Overrides:
typeCheck
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextInfo
- Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.- 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)
-
optimize
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException Optimize the expression- Overrides:
optimize
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextInfo
- 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)
-
getImplementationMethod
public int getImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.- Specified by:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
-
equals
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
- Parameters:
other
- the other operand; the result is false if this is not an Expression- Returns:
- true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
-
computeHashCode
protected int computeHashCode()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:
computeHashCode
in classUnaryExpression
- Returns:
- a computed hash code
-
getItemType
Determine the data type of the result of the Castable expression- Overrides:
getItemType
in classUnaryExpression
- Returns:
- the item type of the items in the result sequence, insofar as this is known statically.
-
getStaticUType
Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.- Overrides:
getStaticUType
in classExpression
- Parameters:
contextItemType
- the static type of the context item- Returns:
- the static item type of the expression according to the XSLT 3.0 defined rules: always xs:boolean
-
computeCardinality
protected 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
. May also returnStaticProperty.ALLOWS_ZERO
if the result is known to be an empty sequence, orStaticProperty.ALLOWS_MANY
if if is known to return a sequence of length two or more.
-
copy
Description copied from class:Expression
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Parameters:
rebindings
- a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.- Returns:
- the copy of the original expression
-
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
-
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
-
getExpressionName
Description copied from class:Expression
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the 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. 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
-
export
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
export
in interfaceExportAgent
- Overrides:
export
in classUnaryExpression
- Parameters:
out
- the expression presenter used to display the structure- Throws:
XPathException
- if the export fails, for example if an expression is found that won't work in the target environment.
-
getElaborator
Make an elaborator for this expression- Overrides:
getElaborator
in classExpression
- Returns:
- an appropriate
Elaborator
-