net.sf.saxon.expr

Class CastExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, 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.

Field Summary

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

operand

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

CastExpression(Expression source, AtomicType target, boolean allowEmpty)
Create a cast expression

Method Summary

boolean
allowsEmpty()
Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)
static AtomicValue
castStringToQName(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
Expression
copy()
Copy an expression.
boolean
equals(Object other)
Is this expression the same as another expression?
Item
evaluateItem(XPathContext context)
Evaluate the expression
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
ItemType
getItemType(TypeHierarchy th)
Get the static type of the expression
AtomicType
getTargetPrimitiveType()
Get the primitive base type of the target type of the cast
AtomicType
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 possible
boolean
isUpCast()
Ask whether this is a cast to a supertype of the original type
Expression
simplify(ExpressionVisitor visitor)
Simplify the expression
boolean
targetIsDerived()
Ask whether the target type is a derived type (not a primitive type)
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

computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, explain, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

CastExpression

public CastExpression(Expression source,
                      AtomicType target,
                      boolean allowEmpty)
Create a cast expression
Parameters:
source - expression giving the value to be converted
target - the type to which the value is to be converted
allowEmpty - 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.

Method Details

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

castStringToQName

public static AtomicValue castStringToQName(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 converted
targetType - the type to which it is to be converted
env - 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

computeCardinality

public int computeCardinality()
Get the static cardinality of the expression
Overrides:
computeCardinality in interface UnaryExpression

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression
Overrides:
computeSpecialProperties in interface UnaryExpression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

equals

public boolean equals(Object other)
Is this expression the same as another expression?
Overrides:
equals in interface UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate the expression
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

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 interface UnaryExpression

getItemType

public ItemType getItemType(TypeHierarchy th)
Get the static type of the expression
Overrides:
getItemType in interface UnaryExpression
Parameters:
th - the type hierarchy cache

getTargetPrimitiveType

public AtomicType getTargetPrimitiveType()
Get the primitive base type of the target type of the cast
Returns:
the primitive type of the target type

getTargetType

public AtomicType getTargetType()
Get the target type (the result type)
Returns:
the target type

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)

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

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify the expression
Overrides:
simplify in interface UnaryExpression
Parameters:
visitor - an expression visitor
Returns:
the simplified expression

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

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 interface UnaryExpression

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression
Overrides:
typeCheck in interface UnaryExpression