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:

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

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 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

CastExpression(Expression source, AtomicType target, boolean allowEmpty)

Method Summary

int	computeCardinality() Get the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
protected java.lang.String	displayOperator(NamePool pool) Give a string representation of the operator for use in diagnostics
AtomicValue	doQNameCast(StaticContext env) Handle a cast to QName or NOTATION.
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

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, 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, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

CastExpression

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

Method Detail

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)

doQNameCast

public AtomicValue doQNameCast(StaticContext env)
                        throws XPathException

Handle a cast to QName or NOTATION. The argument must be a string literal.

Throws:

XPathException

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify the expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class UnaryExpression

Returns:

the simplified expression

Throws:

XPathException

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

Throws:

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(NamePool pool)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Returns:

the operator, as a string