Class ForEach
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.instruct.Instruction
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- net.sf.saxon.expr.instruct.ForEach
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- All Implemented Interfaces:
ContextMappingFunction,ContextOriginator,ContextSwitchingExpression,ExportAgent,TailCallReturner,Locatable,IdentityComparable,Traceable
- Direct Known Subclasses:
MultithreadedForEach
public class ForEach extends Instruction implements ContextMappingFunction, ContextSwitchingExpression
Handler for xsl:for-each elements in a stylesheet. The same class handles the "!" operator in XPath 3.0, which has identical semantics to xsl:for-each, and it is used to support the "/" operator in cases where it is known that the rhs delivers atomic values.
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Field Summary
Fields Modifier and Type Field Description protected OperandactionOpprotected booleancontainsTailCallprotected booleanisInstructionprotected OperandselectOpprotected OperandseparatorOpprotected OperandthreadsOp-
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD
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Constructor Summary
Constructors Constructor Description ForEach(Expression select, Expression action)Create an xsl:for-each instructionForEach(Expression select, Expression action, boolean containsTailCall, Expression threads)Create an xsl:for-each instruction
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description PathMap.PathMapNodeSetaddToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)Add a representation of this expression to a PathMap.booleanalwaysCreatesNewNodes()Ask whether it is guaranteed that every item in the result of this instruction is a newly created node.voidcheckForUpdatingSubexpressions()Check to ensure that this expression does not contain any inappropriate updating subexpressions.voidcheckPermittedContents(SchemaType parentType, boolean whole)Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.intcomputeSpecialProperties()Get the static properties of this expression (other than its type).Expressioncopy(RebindingMap rebindings)Copy an expression.voidevaluatePendingUpdates(XPathContext context, PendingUpdateList pul)Evaluate an updating expression, adding the results to a Pending Update List.protected voidexplainThreads(ExpressionPresenter out)voidexport(ExpressionPresenter out)Diagnostic print of expression structure.ExpressiongetAction()Get the action expression (in XSLT, the body of the xsl:for-each instructionExpressiongetActionExpression()Get the subexpression that is evaluated in the new contextjava.lang.StringgetExpressionName()Get a name identifying the kind of expression, in terms meaningful to a user.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().intgetInstructionNameCode()Get the name of this instruction for diagnostic and tracing purposesItemTypegetItemType()Determine the data type of the items returned by this expressionExpressiongetNumberOfThreadsExpression()Get the number of threads requestedExpressiongetSelect()Get the select expressionExpressiongetSelectExpression()Get the select expressionExpressiongetSeparatorExpression()UTypegetStaticUType(UType contextItemType)Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.java.lang.StringgetStreamerName()Get the (partial) name of a class that supports streaming of this kind of expressionExpressiongetThreads()Get the expression used to determine how many threads to use when multi-threadingbooleanisInstruction()Ask whether this expression is an instruction.booleanisUpdatingExpression()Determine whether this is an updating expression as defined in the XQuery update specificationSequenceIteratoriterate(XPathContext context)Return an Iterator to iterate over the values of the sequence.protected NodeInfomakeSeparator(XPathContext context)SequenceIteratormap(XPathContext context)Map one item to a sequence.booleanmayCreateNewNodes()Determine whether this instruction creates new nodes.java.lang.Iterable<Operand>operands()Get the operands of this expressionExpressionoptimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Perform optimisation of an expression and its subexpressions.TailCallprocessLeavingTail(Outputter output, XPathContext context)ProcessLeavingTail: called to do the real work of this instruction.voidsetAction(Expression action)Set the action expression (in XSLT, the body of the xsl:for-each instruction)voidsetActionExpression(Expression action)Set the action expressionvoidsetInstruction(boolean inst)Say whether this ForEach expression originates as an XSLT instructionvoidsetSelect(Expression select)Set the select expressionvoidsetSelectExpression(Expression select)Set the select expressionvoidsetSeparatorExpression(Expression separator)Set the separator expression (Saxon extension)voidsetThreads(Expression threads)Set the expression used to determine how many threads to use when multi-threadingjava.lang.StringtoShortString()Produce a short string identifying the expression for use in error messagesjava.lang.StringtoString()The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.ExpressiontypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Perform type checking of an expression and its subexpressions.Expressionunordered(boolean retainAllNodes, boolean forStreaming)Replace this expression by a simpler expression that delivers the results without regard to order.-
Methods inherited from class net.sf.saxon.expr.instruct.Instruction
assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, evaluateItem, getNetCost, getSourceLocator, isXSLT, process, someOperandCreatesNewNodes
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Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, computeDependencies, computeHashCode, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, verifyParentPointers
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Detail
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ForEach
public ForEach(Expression select, Expression action)
Create an xsl:for-each instruction- Parameters:
select- the select expressionaction- the body of the xsl:for-each loop
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ForEach
public ForEach(Expression select, Expression action, boolean containsTailCall, Expression threads)
Create an xsl:for-each instruction- Parameters:
select- the select expressionaction- the body of the xsl:for-each loopcontainsTailCall- true if the body of the loop contains a tail call on the containing functionthreads- if >1 causes multithreaded execution (Saxon-EE only)
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Method Detail
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setSeparatorExpression
public void setSeparatorExpression(Expression separator)
Set the separator expression (Saxon extension)
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getSeparatorExpression
public Expression getSeparatorExpression()
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setInstruction
public void setInstruction(boolean inst)
Say whether this ForEach expression originates as an XSLT instruction- Parameters:
inst- true if this is an xsl:for-each instruction; false if it is the XPath "!" operator
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isInstruction
public boolean isInstruction()
Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs.- Overrides:
isInstructionin classInstruction- Returns:
- true if this construct originates as an XSLT instruction
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getSelect
public Expression getSelect()
Get the select expression- Returns:
- the select expression. Note this will have been wrapped in a sort expression if sorting was requested.
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setSelect
public void setSelect(Expression select)
Set the select expression- Parameters:
select- the select expression of the for-each
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getAction
public Expression getAction()
Get the action expression (in XSLT, the body of the xsl:for-each instruction- Returns:
- the action expression
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setAction
public void setAction(Expression action)
Set the action expression (in XSLT, the body of the xsl:for-each instruction)- Parameters:
action- the action expression
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getThreads
public Expression getThreads()
Get the expression used to determine how many threads to use when multi-threading- Returns:
- the saxon:threads expression if present, or null otherwise
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setThreads
public void setThreads(Expression threads)
Set the expression used to determine how many threads to use when multi-threading- Parameters:
threads- the saxon:threads expression if present, or null otherwise
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operands
public java.lang.Iterable<Operand> operands()
Get the operands of this expression- Specified by:
operandsin classInstruction- Returns:
- the operands
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getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes- Overrides:
getInstructionNameCodein classInstruction- Returns:
- the code for name xsl:for-each
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getSelectExpression
public Expression getSelectExpression()
Get the select expression- Specified by:
getSelectExpressionin interfaceContextSwitchingExpression- Returns:
- the select expression. Note this will have been wrapped in a sort expression if sorting was requested.
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setSelectExpression
public void setSelectExpression(Expression select)
Set the select expression- Parameters:
select- the select expression
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setActionExpression
public void setActionExpression(Expression action)
Set the action expression- Parameters:
action- the select expression
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getActionExpression
public Expression getActionExpression()
Get the subexpression that is evaluated in the new context- Specified by:
getActionExpressionin interfaceContextSwitchingExpression- Returns:
- the subexpression evaluated in the context set by the controlling expression
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getNumberOfThreadsExpression
public Expression getNumberOfThreadsExpression()
Get the number of threads requested- Returns:
- the value of the saxon:threads attribute
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getItemType
public final ItemType getItemType()
Determine the data type of the items returned by this expression- Overrides:
getItemTypein classInstruction- Returns:
- the data type
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getStaticUType
public UType getStaticUType(UType contextItemType)
Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.- Overrides:
getStaticUTypein classExpression- Parameters:
contextItemType- static type of the context item- Returns:
- the static item type of the expression according to the XSLT 3.0 defined rules
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mayCreateNewNodes
public final boolean mayCreateNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).- Overrides:
mayCreateNewNodesin classInstruction- Returns:
- true if the instruction creates new nodes under some input conditions (or if it can't be proved that it doesn't)
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Description copied from class:ExpressionPerform type checking of an expression and its subexpressions. This is the second phase of static optimization.This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
- Overrides:
typeCheckin classExpression- Parameters:
visitor- an expression visitorcontextInfo- Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException- if an error is discovered during this phase (typically a type error)
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optimize
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Description copied from class:ExpressionPerform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
- Overrides:
optimizein classExpression- Parameters:
visitor- an expression visitorcontextInfo- 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 toType.ITEM_TYPE- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
XPathException- if an error is discovered during this phase (typically a type error)
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unordered
public Expression unordered(boolean retainAllNodes, boolean forStreaming) throws XPathException
Replace this expression by a simpler expression that delivers the results without regard to order.- Overrides:
unorderedin classExpression- Parameters:
retainAllNodes- set to true if the result must contain exactly the same nodes as the original; set to false if the result can eliminate (or introduce) duplicates.forStreaming- set to true if optimizing for streaming- Returns:
- an expression that delivers the same nodes in a more convenient order
- Throws:
XPathException- if the rewrite fails
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addToPathMap
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.
- Overrides:
addToPathMapin classExpression- Parameters:
pathMap- the PathMap to which the expression should be addedpathMapNodeSet- the set of nodes in the path map that are affected- Returns:
- the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.
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copy
public Expression copy(RebindingMap rebindings)
Copy an expression. This makes a deep copy.- Specified by:
copyin classExpression- Parameters:
rebindings- variables that need to be re-bound- Returns:
- the copy of the original expression
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computeSpecialProperties
public int computeSpecialProperties()
Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.- Overrides:
computeSpecialPropertiesin classInstruction- Returns:
- a set of flags indicating static properties of this expression
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alwaysCreatesNewNodes
public boolean alwaysCreatesNewNodes()
Description copied from class:InstructionAsk whether it is guaranteed that every item in the result of this instruction is a newly created node.- Overrides:
alwaysCreatesNewNodesin classInstruction- Returns:
- true if result of the instruction is always either an empty sequence or a sequence consisting entirely of newly created nodes
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isUpdatingExpression
public boolean isUpdatingExpression()
Determine whether this is an updating expression as defined in the XQuery update specification- Overrides:
isUpdatingExpressionin classExpression- Returns:
- true if this is an updating expression
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checkForUpdatingSubexpressions
public void checkForUpdatingSubexpressions() throws XPathExceptionCheck to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.- Overrides:
checkForUpdatingSubexpressionsin classExpression- Throws:
XPathException- if the expression has a non-permitted updating subexpression
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getImplementationMethod
public int getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both iterate() and process() methods natively.- Overrides:
getImplementationMethodin classInstruction- Returns:
- the implementation method, for example
Expression.ITERATE_METHODorExpression.EVALUATE_METHODorExpression.PROCESS_METHOD
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checkPermittedContents
public void checkPermittedContents(SchemaType parentType, boolean whole) throws XPathException
Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.- Overrides:
checkPermittedContentsin classExpression- Parameters:
parentType- the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this typewhole- if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content- Throws:
XPathException- if the value delivered by this expression cannot be part of the content model of the given type
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processLeavingTail
public TailCall processLeavingTail(Outputter output, XPathContext context) throws XPathException
Description copied from class:InstructionProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.- Specified by:
processLeavingTailin interfaceTailCallReturner- Specified by:
processLeavingTailin classInstruction- Parameters:
output- the destination for the resultcontext- The dynamic context of the transformation, giving access to the current node, the current variables, etc.- Returns:
- null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
- Throws:
XPathException- if a dynamic error occurs during the evaluation of the instruction
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makeSeparator
protected NodeInfo makeSeparator(XPathContext context) throws XPathException
- Throws:
XPathException
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Return an Iterator to iterate over the values of the sequence.- Overrides:
iteratein classInstruction- 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
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map
public SequenceIterator map(XPathContext context) throws XPathException
Map one item to a sequence.- Specified by:
mapin interfaceContextMappingFunction- Parameters:
context- The processing context. The item to be mapped is the context item identified from this context: the values of position() and last() also relate to the set of items being mapped- Returns:
- a SequenceIterator over the sequence of items that the supplied input item maps to
- Throws:
XPathException- if a dynamic error is detected
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evaluatePendingUpdates
public void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException
Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException- Overrides:
evaluatePendingUpdatesin classExpression- Parameters:
context- the XPath dynamic evaluation contextpul- the pending update list to which the results should be written- Throws:
XPathException- if evaluation failsjava.lang.UnsupportedOperationException- if the expression is not an updating expression
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export
public void export(ExpressionPresenter out) throws XPathException
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
exportin interfaceExportAgent- Specified by:
exportin classExpression- Parameters:
out- the expression presenter used to display the structure- Throws:
XPathException- if the export fails, for example if an expression is found that won't work in the target environment.
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explainThreads
protected void explainThreads(ExpressionPresenter out) throws XPathException
- Throws:
XPathException
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toString
public java.lang.String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.
For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression
- Overrides:
toStringin classExpression- Returns:
- a representation of the expression as a string
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toShortString
public java.lang.String toShortString()
Description copied from class:ExpressionProduce a short string identifying the expression for use in error messages- Overrides:
toShortStringin classExpression- Returns:
- a short string, sufficient to identify the expression
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionNamein classInstruction- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
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getStreamerName
public java.lang.String getStreamerName()
Get the (partial) name of a class that supports streaming of this kind of expression- Overrides:
getStreamerNamein classExpression- Returns:
- the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class
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