Package net.sf.saxon.expr
Class ForExpression
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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- net.sf.saxon.expr.Assignation
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- net.sf.saxon.expr.ForExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,Binding
,Container
,Expression
,InstructionInfoProvider
public class ForExpression extends Assignation
A ForExpression maps an expression over a sequence. This version works with range variables, it doesn't change the context information- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.Assignation
action, declaration, nameCode, sequence, slotNumber, variableName
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Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors Constructor Description ForExpression()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
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
computeCardinality()
Determine the static cardinality of the expressionExpression
convertWhereToPredicate(Optimizer opt, StaticContext env, ItemType contextItemType)
Convert where clause, if possible, to a predicate.void
display(int level, java.io.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
getConstructType()
Get the type of this expression for use in tracing and diagnosticsint
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possibleint
getPositionVariableNameCode()
int
getRequiredSlots()
Get the number of slots required.SequenceIterator
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.Expression
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
setPositionVariable(RangeVariableDeclaration decl)
Set the reference to the position variable (XQuery only)void
setSlotNumber(int nr)
Set the slot number for the range variableExpression
typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression-
Methods 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
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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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Method Detail
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setPositionVariable
public void setPositionVariable(RangeVariableDeclaration decl)
Set the reference to the position variable (XQuery only)
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getPositionVariableNameCode
public int getPositionVariableNameCode()
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setAction
public void setAction(Expression action)
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
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
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:
StaticError
- if an error is discovered during this phase (typically a type error)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:
StaticError
- if an error is discovered during this phase (typically a type error)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
protected Binding[] extendBindingList(Binding[] in)
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
public SequenceIterator iterate(XPathContext context) throws XPathException
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
public void process(XPathContext context) throws XPathException
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
public ItemType getItemType(TypeHierarchy th)
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
public void display(int level, java.io.PrintStream out, Configuration config)
Diagnostic print of expression structure- Parameters:
level
- indentation level for this expressionout
- Output destination
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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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