net.sf.saxon.expr

Class CastToUnion

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.CastToUnion

All Implemented Interfaces:

IdentityComparable

public class CastToUnion
extends UnaryExpression

Expression class for a cast to a union type

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
CastToUnion(Expression source, UnionType targetType, boolean allowEmpty) Create a cast expression to a union type

Method Summary

Methods

Modifier and Type	Method and Description
static AtomicSequence	cast(AtomicValue value, UnionType targetType, NamespaceResolver nsResolver, ConversionRules rules) Static method to perform the cast of an atomic value to a union type
static boolean	castable(AtomicValue value, UnionType targetType, NamespaceResolver nsResolver, XPathContext context) Static method to perform the castable check of an atomic value to a union type
int	computeCardinality() Get the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
Expression	copy() Copy an expression.
boolean	equals(Object other) Is this expression the same as another expression?
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
CastToUnionCompiler	getExpressionCompiler() Return the compiler of the CastToUnion expression
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType() Get the static type of the expression
NamespaceResolver	getNamespaceResolver() Get the namespace resolver that will be used to resolve any namespace-sensitive values (such as QNames) when casting
protected OperandRole	getOperandRole() Get the usage (in terms of streamability analysis) of the single operand
UnionType	getTargetType() Get the union type that is the target of this cast operation
int	hashCode() get HashCode for comparing two expressions.
boolean	isAllowEmpty() Ask whether the value of the operand is allowed to be empty
SequenceIterator	iterate(XPathContext context) Evaluate the expression
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform optimisation of an expression and its subexpressions.
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, ContextItemStaticInfo contextInfo) Type-check the expression

Methods inherited from class net.sf.saxon.expr.UnaryExpression

displayOperator, getBaseExpression, getOperand, operands, setBaseExpression, toShortString

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExpressionName, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getStreamingAdjunct, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, optimizeForType, process, promote, promoteChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeCheckChildren, typeError, unordered

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CastToUnion

public CastToUnion(Expression source,
           UnionType targetType,
           boolean allowEmpty)

Create a cast expression to a union type

Parameters:

source - the operand of the cast

targetType - the union type that is the result of the cast

allowEmpty - true if an empty sequence may be supplied as input, converting to an empty sequence on output

Method Detail

getOperandRole

protected OperandRole getOperandRole()

Get the usage (in terms of streamability analysis) of the single operand

Specified by:

getOperandRole in class UnaryExpression

Returns:

the operand usage

isAllowEmpty

public boolean isAllowEmpty()

Ask whether the value of the operand is allowed to be empty

Returns:

true if an empty sequence may be supplied as input, converting to an empty sequence on output

getTargetType

public UnionType getTargetType()

Get the union type that is the target of this cast operation

Returns:

the target type of the cast

getNamespaceResolver

public NamespaceResolver getNamespaceResolver()

Get the namespace resolver that will be used to resolve any namespace-sensitive values (such as QNames) when casting

Returns:

the namespace resolver, or null if there is none.

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                   ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

visitor - an expression visitor

contextInfo - 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

Perform optimisation of an expression and its subexpressions.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:

optimize in class UnaryExpression

Parameters:

visitor - an expression visitor

contextInfo - 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 to Type.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)

computeCardinality

public int computeCardinality()

Get the static cardinality of the expression

Overrides:

computeCardinality in class UnaryExpression

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

getItemType

public ItemType getItemType()

Get the static type of the expression

Overrides:

getItemType in class UnaryExpression

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NON_CREATIVE.

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

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 class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Evaluate the expression

Overrides:

iterate in class Expression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

castable

public static boolean castable(AtomicValue value,
               UnionType targetType,
               NamespaceResolver nsResolver,
               XPathContext context)

Static method to perform the castable check of an atomic value to a union type

Parameters:

value - the input value to be converted. Must not be null.

targetType - the union type to which the value is to be converted

nsResolver - the namespace context, required if the type is namespace-sensitive

context - the XPath dynamic evaluation context

Returns:

the result of the conversion (may be a sequence if the union includes list types in its membership)

cast

public static AtomicSequence cast(AtomicValue value,
                  UnionType targetType,
                  NamespaceResolver nsResolver,
                  ConversionRules rules)
                           throws XPathException

Static method to perform the cast of an atomic value to a union type

Parameters:

value - the input value to be converted. Must not be null.

targetType - the union type to which the value is to be converted

nsResolver - the namespace context, required if the type is namespace-sensitive

rules - the conversion rules

Returns:

the result of the conversion (may be a sequence if the union includes list types in its membership)

Throws:

XPathException - if the conversion fails

getExpressionCompiler

public CastToUnionCompiler getExpressionCompiler()

Return the compiler of the CastToUnion expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

hashCode

public int hashCode()

get HashCode for comparing two expressions.

Overrides:

hashCode in class UnaryExpression

toString

public 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 class UnaryExpression

Returns:

a representation of the expression as a string

export

public void export(ExpressionPresenter out)

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Overrides:

export in class UnaryExpression

Parameters:

out - the expression presenter used to display the structure