net.sf.saxon.instruct

Class ValueOf

Implemented Interfaces:
SourceLocator, EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator, TailCallReturner

public final class ValueOf
extends SimpleNodeConstructor

An xsl:value-of element in the stylesheet.
The xsl:value-of element takes attributes:

Field Summary

Fields inherited from class net.sf.saxon.instruct.SimpleNodeConstructor

select

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

ValueOf(Expression select, boolean disable, boolean noNodeIfEmpty)
Create a new ValueOf expression

Method Summary

void
checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole)
Check statically that the results of the expression are capable of constructing the content of a given schema type.
int
computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction
Expression
convertToStringJoin(StaticContext env)
Convert this value-of instruction to an expression that delivers the string-value of the resulting text node.
Expression
copy()
Copy an expression.
Item
evaluateItem(XPathContext context)
Evaluate this expression, returning the resulting text node to the caller
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
int
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
int
getOptions()
Test for any special options such as disable-output-escaping
boolean
isNumberingInstruction()
Determine whether this is really an xsl:number instruction
void
localTypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Method to perform type-checking specific to the kind of instruction
TailCall
processLeavingTail(XPathContext context)
Process this instruction, sending the resulting text node to the current output destination
protected void
promoteInst(PromotionOffer offer)
Offer promotion for subexpressions.
void
setIsNumberingInstruction()
Indicate that this is really an xsl:nunber instruction

Methods inherited from class net.sf.saxon.instruct.SimpleNodeConstructor

checkContent, computeCardinality, computeSpecialProperties, createsNewNodes, evaluateItem, evaluateNameCode, expandChildren, getSelect, iterate, iterateSubExpressions, localTypeCheck, optimize, promoteInst, replaceSubExpression, setSelect, simplify, typeCheck

Methods inherited from class net.sf.saxon.instruct.Instruction

assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, evaluateItem, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, iterate, process, processLeavingTail, promote, promoteInst, simplify

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

ValueOf

public ValueOf(Expression select,
               boolean disable,
               boolean noNodeIfEmpty)
Create a new ValueOf expression
Parameters:
select - the select expression
disable - true if disable-output-escaping is in force
noNodeIfEmpty - true if the instruction is to return () if the select expression is (), false if it is to return an empty text node

Method Details

checkPermittedContents

public void checkPermittedContents(SchemaType parentType,
                                   StaticContext env,
                                   boolean whole)
            throws XPathException
Check statically that the results of the expression are capable of constructing the content of a given schema type.
Overrides:
checkPermittedContents in interface Expression
Parameters:
parentType - The schema type
env - the static context
whole - true if this expression is to account for the whole value of the type
Throws:
XPathException - if the expression doesn't match the required content type

computeCardinality

public int computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction
Overrides:
computeCardinality in interface SimpleNodeConstructor
Returns:
the static cardinality

convertToStringJoin

public Expression convertToStringJoin(StaticContext env)
Convert this value-of instruction to an expression that delivers the string-value of the resulting text node. This will often be a call on the string-join function.
Parameters:
env - the static evaluation context
Returns:
the converted expression

copy

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

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate this expression, returning the resulting text node to the caller
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface SimpleNodeConstructor
Parameters:
context - the dynamic evaluation context
Returns:
the parentless text node that results from evaluating this instruction, or null to represent an empty sequence
Throws:
XPathException -

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 Expression

getInstructionNameCode

public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes
Overrides:
getInstructionNameCode in interface Instruction
Returns:
the namecode of the instruction name

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Overrides:
getItemType in interface Instruction
Parameters:
th - the type hierarchy cache
Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

getOptions

public int getOptions()
Test for any special options such as disable-output-escaping
Returns:
any special options

isNumberingInstruction

public boolean isNumberingInstruction()
Determine whether this is really an xsl:number instruction
Returns:
true if this derives from xsl:number

localTypeCheck

public void localTypeCheck(ExpressionVisitor visitor,
                           ItemType contextItemType)
Method to perform type-checking specific to the kind of instruction
Overrides:
localTypeCheck in interface SimpleNodeConstructor
Parameters:
visitor - an expression visitor
contextItemType - the static type of the context item

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
            throws XPathException
Process this instruction, sending the resulting text node to the current output destination
Specified by:
processLeavingTail in interface TailCallReturner
Overrides:
processLeavingTail in interface Instruction
Parameters:
context - the dynamic evaluation context
Returns:
Always returns null
Throws:
XPathException -

promoteInst

protected void promoteInst(PromotionOffer offer)
            throws XPathException
Offer promotion for subexpressions. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.
Overrides:
promoteInst in interface SimpleNodeConstructor
Parameters:
offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
Throws:
XPathException - if any error is detected

setIsNumberingInstruction

public void setIsNumberingInstruction()
Indicate that this is really an xsl:nunber instruction