net.sf.saxon.expr
Class Assignation

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.Assignation

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, Binding, EvaluableItem, SequenceIterable, InstructionInfo, Locator

Direct Known Subclasses:

ForExpression, LetExpression, QuantifiedExpression

public abstract class Assignation
extends Expression
implements Binding

Assignation is an abstract superclass for the kinds of expression that declare range variables: for, some, and every.

See Also:

Serialized Form

Field Summary

protected Expression	action
protected SequenceType	requiredType
protected Expression	sequence
protected int	slotNumber
protected StructuredQName	variableName

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

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

Assignation()

Method Summary

void	addReference(boolean isLoopingReference) Register a variable reference that refers to the variable bound in this expression
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
void	checkForUpdatingSubexpressions() Check to ensure that this expression does not contain any inappropriate updating subexpressions.
ValueRepresentation	evaluateVariable(XPathContext context) Get the value of the range variable
Binding[]	extendBindingList(Binding[] in) Extend an array of variable bindings to include the binding(s) defined in this expression
Expression	getAction() Get the action expression
int	getLocalSlotNumber() If this is a local variable held on the local stack frame, return the corresponding slot number.
int	getNominalReferenceCount() Get the (nominal) count of the number of references to this variable
StructuredQName	getObjectName() Get a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc.
int	getRequiredSlots() Get the number of slots required.
SequenceType	getRequiredType() Get the declared type of the variable
Expression	getSequence() Get the "sequence" expression - the one to which the variable is bound
String	getVariableName() Get the display name of the range variable, for diagnostics only
StructuredQName	getVariableQName() Get the name of the variable
boolean	isAssignable() Test whether it is permitted to assign to the variable using the saxon:assign extension element.
boolean	isGlobal() Indicate whether the binding is local or global.
boolean	isIndexedVariable() Test whether the variable bound by this let expression should be indexable
boolean	isUpdatingExpression() Determine whether this is an updating expression as defined in the XQuery update specification
Iterator<Expression>	iterateSubExpressions() Get the immediate subexpressions of this expression
Expression	promote(PromotionOffer offer, Expression parent) Promote this expression if possible
protected Expression	promoteWhereClause(Binding positionBinding) Promote a WHERE clause whose condition doesn't depend on the variable being bound.
void	refineTypeInformation(ItemType type, int cardinality, Value constantValue, int properties, ExpressionVisitor visitor, Assignation currentExpression) Refine the type information associated with this variable declaration.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
void	replaceVariable(Optimizer opt, Expression seq) Replace all references to the variable bound by this let expression, that occur within the action expression, with the given expression
void	setAction(Expression action) Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression
void	setIndexedVariable() Indicate that the variable bound by this let expression should be indexable (because it is used in an appropriate filter expression)
void	setRequiredType(SequenceType requiredType) Set the required type (declared type) of the variable
void	setSequence(Expression sequence) Set the "sequence" expression - the one to which the variable is bound
void	setSlotNumber(int nr) Set the slot number for the range variable
void	setVariableQName(StructuredQName variableName) Set the name of the variable
Expression	simplify(ExpressionVisitor visitor) Simplify the expression
void	suppressValidation(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.

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

adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getItemType, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, optimize, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, toString, typeCheck, typeError

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

slotNumber

protected int slotNumber

sequence

protected Expression sequence

action

protected Expression action

variableName

protected StructuredQName variableName

requiredType

protected SequenceType requiredType

Constructor Detail

Assignation

public Assignation()

Method Detail

setRequiredType

public void setRequiredType(SequenceType requiredType)

Set the required type (declared type) of the variable

Parameters:

requiredType - the required type

setVariableQName

public void setVariableQName(StructuredQName variableName)

Set the name of the variable

Parameters:

variableName - the name of the variable

getVariableQName

public StructuredQName getVariableQName()

Get the name of the variable

Specified by:

getVariableQName in interface Binding

Returns:

the variable name, as a QName

getObjectName

public StructuredQName getObjectName()

Description copied from interface: InstructionInfo

Get a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc. This is used only where the name is known statically.

Specified by:

getObjectName in interface InstructionInfo

Overrides:

getObjectName in class Expression

Returns:

the QName of the object declared or manipulated by this instruction or expression

getRequiredType

public SequenceType getRequiredType()

Get the declared type of the variable

Specified by:

getRequiredType in interface Binding

Returns:

the declared type

getLocalSlotNumber

public int getLocalSlotNumber()

If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.

Specified by:

getLocalSlotNumber in interface Binding

Returns:

the slot number on the local stack frame

evaluateVariable

public ValueRepresentation evaluateVariable(XPathContext context)
                                     throws XPathException

Get the value of the range variable

Specified by:

evaluateVariable in interface Binding

Parameters:

context - the XPath dynamic evaluation context

Returns:

the result of evaluating the variable

Throws:

XPathException

setAction

public void setAction(Expression action)

Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression

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.

isGlobal

public final boolean isGlobal()

Indicate whether the binding is local or global. A global binding is one that has a fixed value for the life of a query or transformation; any other binding is local.

Specified by:

isGlobal in interface Binding

Returns:

true if the binding is global

isAssignable

public final boolean isAssignable()

Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be for an XSLT global variable where the extra attribute saxon:assignable="yes" is present.

Specified by:

isAssignable in interface Binding

Returns:

true if the binding is assignable

checkForUpdatingSubexpressions

public void checkForUpdatingSubexpressions()
                                    throws XPathException

Check to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.

Overrides:

checkForUpdatingSubexpressions in class Expression

Throws:

XPathException - if the expression has a non-permitted updateing subexpression

isUpdatingExpression

public boolean isUpdatingExpression()

Determine whether this is an updating expression as defined in the XQuery update specification

Overrides:

isUpdatingExpression in class Expression

Returns:

true if this is an updating expression

getAction

public Expression getAction()

Get the action expression

Returns:

the action expression (introduced by "return" or "satisfies")

setSequence

public void setSequence(Expression sequence)

Set the "sequence" expression - the one to which the variable is bound

Parameters:

sequence - the expression to which the variable is bound

getSequence

public Expression getSequence()

Get the "sequence" expression - the one to which the variable is bound

Returns:

the expression to which the variable is bound

setSlotNumber

public void setSlotNumber(int nr)

Set the slot number for the range variable

Parameters:

nr - the slot number to be used

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.

Returns:

the number of slots required

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Simplify the expression

Overrides:

simplify in class Expression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

promote

public Expression promote(PromotionOffer offer,
                          Expression parent)
                   throws XPathException

Promote this expression if possible

Overrides:

promote in class Expression

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

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

suppressValidation

public void suppressValidation(int validationMode)

Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation. The default implementation does nothing.

Overrides:

suppressValidation in class Expression

Parameters:

validationMode - the kind of validation being performed on the parent expression

extendBindingList

public Binding[] extendBindingList(Binding[] in)

Extend an array of variable bindings to include the binding(s) defined in this expression

Parameters:

in - a set of variable bindings

Returns:

a set of variable bindings including all those supplied plus this one

promoteWhereClause

protected Expression promoteWhereClause(Binding positionBinding)

Promote a WHERE clause whose condition doesn't depend on the variable being bound. This rewrites an expression of the form

let $i := SEQ return if (C) then R else ()

to the form:

if (C) then (let $i := SEQ return R) else ()

Parameters:

positionBinding - the binding of the position variable if any

Returns:

an expression in which terms from the WHERE clause that can be extracted have been extracted

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()

Get the immediate subexpressions of this expression

Overrides:

iterateSubExpressions in class Expression

Returns:

an iterator containing the sub-expressions of this expression

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)

Replace one subexpression by a replacement subexpression

Overrides:

replaceSubExpression in class Expression

Parameters:

original - the original subexpression

replacement - the replacement subexpression

Returns:

true if the original subexpression is found

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:

addToPathMap in class Expression

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added

Returns:

the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this 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.

getVariableName

public String getVariableName()

Get the display name of the range variable, for diagnostics only

Returns:

the lexical QName of the range variable

refineTypeInformation

public void refineTypeInformation(ItemType type,
                                  int cardinality,
                                  Value constantValue,
                                  int properties,
                                  ExpressionVisitor visitor,
                                  Assignation currentExpression)

Refine the type information associated with this variable declaration. This is useful when the type of the variable has not been explicitly declared (which is common); the variable then takes a static type based on the type of the expression to which it is bound. The effect of this call is to update the static expression type for all references to this variable.

Parameters:

type - the inferred item type of the expression to which the variable is bound

cardinality - the inferred cardinality of the expression to which the variable is bound

constantValue - the constant value to which the variable is bound (null if there is no constant value)

properties - other static properties of the expression to which the variable is bound

visitor - an expression visitor to provide context information

currentExpression - the expression that binds the variable

addReference

public void addReference(boolean isLoopingReference)

Register a variable reference that refers to the variable bound in this expression

Parameters:

isLoopingReference - - true if the reference occurs within a loop, such as the predicate of a filter expression

getNominalReferenceCount

public int getNominalReferenceCount()

Get the (nominal) count of the number of references to this variable

Returns:

zero if there are no references, one if there is a single reference that is not in a loop, some higher number if there are multiple references (or a single reference in a loop), or the special value @link RangeVariable#FILTERED} if there are any references in filter expressions that require searching.

isIndexedVariable

public boolean isIndexedVariable()

Test whether the variable bound by this let expression should be indexable

Returns:

true if the variable should be indexable

replaceVariable

public void replaceVariable(Optimizer opt,
                            Expression seq)
                     throws XPathException

Replace all references to the variable bound by this let expression, that occur within the action expression, with the given expression

Parameters:

opt - The optimizer

seq - the expression

Throws:

XPathException

setIndexedVariable

public void setIndexedVariable()

Indicate that the variable bound by this let expression should be indexable (because it is used in an appropriate filter expression)