Class While
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.instruct.Instruction
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- net.sf.saxon.instruct.While
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,TailCallReturner
,InstructionInfo
,org.xml.sax.Locator
public class While extends Instruction
Handler for saxon:while elements in stylesheet.
The saxon:while element has a mandatory attribute test, a boolean expression. The content is output repeatedly so long as the test condition is true.- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description While(Expression test, Expression action)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Expression
copy()
Copy an expression.boolean
createsNewNodes()
Determine whether this instruction creates new nodes.void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.Expression
getActionExpression()
Get the action expression (the content of the for-each)int
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposesItemType
getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instructionboolean
hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedlyjava.util.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(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.TailCall
processLeavingTail(XPathContext context)
ProcessLeavingTail: called to do the real work of this instruction.protected void
promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
simplify(ExpressionVisitor visitor)
Simplify an expression.Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.-
Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getConstructType, getImplementationMethod, getSourceLocator, isXSLT, iterate, process, promote
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
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Constructor Detail
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While
public While(Expression test, Expression action)
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Method Detail
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getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes- Overrides:
getInstructionNameCode
in classInstruction
- Returns:
- the string "saxon:while"
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getActionExpression
public Expression getActionExpression()
Get the action expression (the content of the for-each)
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).- Specified by:
simplify
in classInstruction
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Description copied from class:Expression
Perform 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.
If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
- Overrides:
typeCheck
in classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 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, ItemType contextItemType) throws XPathException
Description copied from class:Expression
Perform 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:
optimize
in classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction- Overrides:
getItemType
in classInstruction
- Parameters:
th
- the type hierarchy cache- Returns:
- the static item type of the instruction
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promoteInst
protected void promoteInst(PromotionOffer offer) throws XPathException
Handle promotion offers, that is, non-local tree rewrites.- Overrides:
promoteInst
in classInstruction
- Parameters:
offer
- The type of rewrite being offered- Throws:
XPathException
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createsNewNodes
public final boolean createsNewNodes()
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:
createsNewNodes
in classInstruction
- Returns:
- true if the instruction creates new nodes (or if it can't be proved that it doesn't)
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iterateSubExpressions
public java.util.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)- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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hasLoopingSubexpression
public boolean hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly- Overrides:
hasLoopingSubexpression
in classExpression
- Parameters:
child
- the immediate subexpression- Returns:
- true if the child expression is evaluated repeatedly
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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processLeavingTail
public TailCall processLeavingTail(XPathContext context) throws XPathException
Description copied from class:Instruction
ProcessLeavingTail: 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:
processLeavingTail
in interfaceTailCallReturner
- Specified by:
processLeavingTail
in classInstruction
- Parameters:
context
- 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
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explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
explain
in classExpression
- Parameters:
out
- the expression presenter used to display the structure
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