net.sf.saxon.expr

Class CastExpression

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.CastExpression

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, Container, Expression, InstructionInfoProvider

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

Field Summary

Fields

Modifier and Type	Field and Description
(package private) static IntHashMap	castingTable

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

operand

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

locationId, staticProperties

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Constructors

Constructor and Description
CastExpression(Expression source, AtomicType target, boolean allowEmpty)

Method Summary

Modifier and Type	Method and Description
(package private) static void	addAllowedCasts(int source, int[] target)
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 expression
int	computeSpecialProperties() Determine the special properties of this expression
protected java.lang.String	displayOperator(Configuration config) Give a string representation of the operator for use in diagnostics
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
Item	evaluateItem(XPathContext context) Evaluate the expression
ItemType	getItemType(TypeHierarchy th) Get the static type of the expression
static boolean	isPossibleCast(int source, int target) Determine whether casting from a source type to a target type is possible
Expression	simplify(StaticContext env) Simplify the expression
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

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

display, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

Field Detail

castingTable

static IntHashMap castingTable

Constructor Detail

CastExpression

public CastExpression(Expression source,
                      AtomicType target,
                      boolean allowEmpty)

Method Detail

addAllowedCasts

static void addAllowedCasts(int source,
                            int[] target)

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)

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify the expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class UnaryExpression

Parameters:

env - the static context

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression

Specified by:

typeCheck in interface Expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

env - the static context of the expression

contextItemType - 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 to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

computeCardinality

public int computeCardinality()

Get the static cardinality of the expression

Overrides:

computeCardinality in class UnaryExpression

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the static type of the expression

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

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.

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

displayOperator

protected java.lang.String displayOperator(Configuration config)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Parameters:

config -

Returns:

the operator, as a string

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

Returns:

the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a DerivedAtomicValue derived from QName or NOTATION

Throws:

XPathException