net.sf.saxon.instruct

Class GeneralVariable

public abstract class GeneralVariable extends Instruction implements Binding

This class defines common behaviour across xsl:variable, xsl:param, and xsl:with-param; also saxon:assign

Field Summary
protected int	nameCode
protected int	referenceCount
SequenceType	requiredType
Expression	select

Constructor Summary
	GeneralVariable()

Method Summary
void	display(int level, NamePool pool, PrintStream out) Diagnostic print of expression structure.
Item	evaluateItem(XPathContext context) Evaluate an expression as a single item.
int	getCardinality() Get the cardinality of the result of this instruction.
int	getInstructionNameCode()
ItemType	getItemType(TypeHierarchy th) Get the type of the result of this instruction.
int	getLocalSlotNumber() If this is a local variable held on the local stack frame, return the corresponding slot number.
int	getNameCode()
SequenceType	getRequiredType()
Expression	getSelectExpression()
ValueRepresentation	getSelectValue(XPathContext context) Evaluate the variable.
int	getSlotNumber()
int	getVariableFingerprint() Get the name of the variable (as a NamePool fingerprint)
String	getVariableName()
void	init(Expression select, int nameCode)
boolean	isAssignable() Test whether it is permitted to assign to the variable using the saxon:assign extension element.
boolean	isGlobal()
boolean	isRequiredParam()
boolean	isTunnelParam()
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
Iterator	iterateSubExpressions() Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
protected void	promoteInst(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.
void	setAssignable(boolean assignable)
void	setNameCode(int nameCode)
void	setReferenceCount(int refCount)
void	setRequiredParam(boolean requiredParam)
void	setRequiredType(SequenceType required)
void	setSelectExpression(Expression select)
void	setSlotNumber(int s)
void	setTunnel(boolean tunnel)
void	setVariableName(String s)
Expression	simplify(StaticContext env)
Expression	typeCheck(StaticContext env, ItemType contextItemType)

Field Detail

Method Detail

display

public void display(int level, NamePool pool, PrintStream out)

Diagnostic print of expression structure. The expression is written to the System.err output stream

Parameters: level indentation level for this expression out

evaluateItem

public Item evaluateItem(XPathContext context)

Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.

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

getCardinality

public int getCardinality()

Get the cardinality of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.

Returns: the empty cardinality.

getInstructionNameCode

public int getInstructionNameCode()

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the type of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.

Parameters: th

Returns: the empty type.

getLocalSlotNumber

public int getLocalSlotNumber()

If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.

getNameCode

public int getNameCode()

getRequiredType

public SequenceType getRequiredType()

getSelectExpression

public Expression getSelectExpression()

getSelectValue

public ValueRepresentation getSelectValue(XPathContext context)

Evaluate the variable. That is, get the value of the select expression if present or the content of the element otherwise, either as a tree or as a sequence

getSlotNumber

public int getSlotNumber()

getVariableFingerprint

public int getVariableFingerprint()

Get the name of the variable (as a NamePool fingerprint)

Returns: the NamePool fingerprint of the variable's expanded name.

getVariableName

public String getVariableName()

init

public void init(Expression select, int nameCode)

isAssignable

public final boolean isAssignable()

Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be true if the extra attribute saxon:assignable="yes" is present.

isGlobal

public boolean isGlobal()

isRequiredParam

public final boolean isRequiredParam()

isTunnelParam

public final boolean isTunnelParam()

iterate

public SequenceIterator iterate(XPathContext context)

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence. In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.

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

Parameters: offer The type of rewrite being offered

Throws: XPathException