Package net.sf.saxon.expr
Class ForExpression
java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.Assignation
net.sf.saxon.expr.ForExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,Binding
,Container
,Expression
,InstructionInfoProvider
A ForExpression maps an expression over a sequence.
This version works with range variables, it doesn't change the context information
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.Assignation
action, declaration, nameCode, sequence, slotNumber, variableName
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
checkPermittedContents
(SchemaType parentType, StaticContext env, 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.int
Determine the static cardinality of the expressionconvertWhereToPredicate
(Optimizer opt, StaticContext env, ItemType contextItemType) Convert where clause, if possible, to a predicate.void
display
(int level, PrintStream out, Configuration config) Diagnostic print of expression structureprotected Binding[]
extendBindingList
(Binding[] in) Extend an array of variable bindings to include the binding(s) defined in this expressionprotected int
Get the type of this expression for use in tracing and diagnosticsint
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Determine the data type of the items returned by the expression, if possibleint
int
Get the number of slots required.iterate
(XPathContext context) Iterate over the sequence of valuesboolean
markTailFunctionCalls
(int nameCode, int arity) Mark tail function calls: only possible if the for expression iterates zero or one times.optimize
(Optimizer opt, StaticContext env, ItemType contextItemType) Optimize the expressionvoid
process
(XPathContext context) Process this expression as an instruction, writing results to the current outputtervoid
setAction
(Expression action) Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expressionvoid
Set the reference to the position variable (XQuery only)void
setSlotNumber
(int nr) Set the slot number for the range variabletypeCheck
(StaticContext env, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.Assignation
evaluateVariable, getAction, getLocalSlotNumber, getSequence, getVariableDeclaration, getVariableFingerprint, getVariableName, getVariableNameCode, isAssignable, isGlobal, iterateSubExpressions, promote, promoteWhereClause, replaceSubExpression, setSequence, setVariableDeclaration, simplify, suppressValidation
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getDependencies, getExecutable, getHostLanguage, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, typeError
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Constructor Details
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ForExpression
public ForExpression()
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Method Details
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setPositionVariable
Set the reference to the position variable (XQuery only) -
getPositionVariableNameCode
public int getPositionVariableNameCode() -
setAction
Description copied from class:Assignation
Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression- Overrides:
setAction
in classAssignation
- Parameters:
action
- the expression that occurs after the "return" keyword of a "for" expression, the "satisfies" keyword of "some/every", or the ":=" operator of a "let" expression.This method must be called after calling setVariableDeclaration()
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setSlotNumber
public void setSlotNumber(int nr) Set the slot number for the range variable- Overrides:
setSlotNumber
in classAssignation
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getRequiredSlots
public int getRequiredSlots()Get the number of slots required. Normally 1, except for a FOR expression with an AT clause, where it is 2.- Overrides:
getRequiredSlots
in classAssignation
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typeCheck
Type-check the expression- Parameters:
env
- the static context of the expressioncontextItemType
- 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
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException Optimize the expression- Parameters:
opt
- the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.env
- the static context of the expressioncontextItemType
- 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
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convertWhereToPredicate
public Expression convertWhereToPredicate(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException Convert where clause, if possible, to a predicate. Returns the converted expression if modified, or null otherwise- Throws:
XPathException
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markTailFunctionCalls
public boolean markTailFunctionCalls(int nameCode, int arity) Mark tail function calls: only possible if the for expression iterates zero or one times. (This arises in XSLT/XPath, which does not have a LET expression, so FOR gets used instead)- Overrides:
markTailFunctionCalls
in classComputedExpression
- Returns:
- true if a tail recursive call was found and if this call accounts for the whole of the value.
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extendBindingList
Extend an array of variable bindings to include the binding(s) defined in this expression- Overrides:
extendBindingList
in classAssignation
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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.- Specified by:
getImplementationMethod
in interfaceExpression
- Overrides:
getImplementationMethod
in classComputedExpression
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checkPermittedContents
public void checkPermittedContents(SchemaType parentType, StaticContext env, 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.- Specified by:
checkPermittedContents
in interfaceExpression
- Overrides:
checkPermittedContents
in classComputedExpression
- Parameters:
parentType
- The schema typeenv
- the static contextwhole
- true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part- Throws:
XPathException
- if the expression doesn't match the required content type
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iterate
Iterate over the sequence of values- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classComputedExpression
- 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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process
Process this expression as an instruction, writing results to the current outputter- Specified by:
process
in interfaceExpression
- Overrides:
process
in classComputedExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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getItemType
Determine the data type of the items returned by the expression, if possible- Parameters:
th
-- Returns:
- one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
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computeCardinality
public int computeCardinality()Determine the static cardinality of the expression- Specified by:
computeCardinality
in classComputedExpression
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display
Diagnostic print of expression structure- Parameters:
level
- indentation level for this expressionout
- Output destinationconfig
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getConstructType
protected int getConstructType()Get the type of this expression for use in tracing and diagnostics- Overrides:
getConstructType
in classComputedExpression
- Returns:
- the type of expression, as enumerated in class
Location
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