net.sf.saxon.expr

Class Assignation

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.Assignation

All Implemented Interfaces:

Binding, ExportAgent, LocalBinding, Locatable, IdentityComparable

Direct Known Subclasses:

ForExpression, LetExpression, QuantifiedExpression

public abstract class Assignation
extends Expression
implements LocalBinding

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

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	hasLoopingReference
protected boolean	isIndexedVariable
protected java.util.List<VariableReference>	references
protected SequenceType	requiredType
protected int	slotNumber
protected StructuredQName	variableName

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

Constructor Summary

Constructors

Constructor and Description
Assignation()

Method Summary

Modifier and Type	Method and Description
void	addReference(VariableReference ref, 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.
int	computeDependencies() Compute the dependencies of an expression, as the union of the dependencies of its sub-expressions.
Sequence<?>	evaluateVariable(XPathContext context) Get the value of the range variable
Expression	getAction() Get the action expression
Operand	getActionOp()
double	getCost() Return the estimated cost of evaluating an expression.
IntegerValue[]	getIntegerBoundsForVariable() If the variable is bound to an integer, get the minimum and maximum possible values.
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()
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
Operand	getSequenceOp()
java.lang.String	getVariableEQName() Get the name of the range variable as a Name or EQName.
java.lang.String	getVariableName() Get the display name of the range variable, for diagnostics only
StructuredQName	getVariableQName() Get the name of the variable
boolean	hasVariableBinding(Binding binding) Ask whether this expression is, or contains, the binding of a given 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
java.lang.Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
void	rebuildReferenceList(boolean force) Rebuild the reference list to guide subsequent optimization.
void	refineTypeInformation(ItemType type, int cardinality, GroundedValue<?> constantValue, int properties, Assignation currentExpression) Refine the type information associated with this variable declaration.
protected boolean	removeDeadReferences() Remove dead references from the reference list of the variable; at the same time, check whether any of the variable references is in a loop, and return true if so.
boolean	replaceVariable(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
void	suppressValidation(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.
Expression	unordered(boolean retainAllNodes, boolean forStreaming) Replace this expression by a simpler expression that delivers the results without regard to order.
protected void	verifyReferences() This method recomputes the reference list by scanning the subtree rooted at this variable binding.

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

adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkPermittedContents, computeCardinality, computeHashCode, computeSpecialProperties, computeStaticProperties, copy, dynamicError, effectiveBooleanValue, equals, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, export, getCardinality, getConfiguration, getConstructType, getDependencies, getEvaluationMethod, getExpressionName, getExtraProperty, getImplementationMethod, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getItemType, getLocalRetainedStaticContext, getLocation, getNetCost, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasSpecialProperty, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, toPattern, toShortString, toString, typeCheck, typeCheckChildren, typeError, verifyParentPointers

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

slotNumber

protected int slotNumber

variableName

protected StructuredQName variableName

requiredType

protected SequenceType requiredType

isIndexedVariable

protected boolean isIndexedVariable

hasLoopingReference

protected boolean hasLoopingReference

references

protected java.util.List<VariableReference> references

Constructor Detail

Assignation

public Assignation()

Method Detail

getSequenceOp

public Operand getSequenceOp()

getActionOp

public Operand getActionOp()

operands

public java.lang.Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

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()

Overrides:

getObjectName in class Expression

getRequiredType

public SequenceType getRequiredType()

Get the declared type of the variable

Specified by:

getRequiredType in interface Binding

Returns:

the declared type

getIntegerBoundsForVariable

public IntegerValue[] getIntegerBoundsForVariable()

If the variable is bound to an integer, get the minimum and maximum possible values. Return null if unknown or not applicable

Specified by:

getIntegerBoundsForVariable in interface Binding

Returns:

a pair of integers containing the minimum and maximum values for the integer value; or null if the value is not an integer or the range is unknown

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 LocalBinding

Returns:

the slot number on the local stack frame

computeDependencies

public int computeDependencies()

Compute the dependencies of an expression, as the union of the dependencies of its sub-expressions. (This is overridden for path expressions and filter expressions, where the dependencies of a sub-expression are not all propagated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.

Overrides:

computeDependencies in class Expression

Returns:

the dependencies, as a bit-mask

evaluateVariable

public Sequence<?> 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 - if an error occurs while evaluating the variable

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

hasVariableBinding

public boolean hasVariableBinding(Binding binding)

Description copied from class: Expression

Ask whether this expression is, or contains, the binding of a given variable

Overrides:

hasVariableBinding in class Expression

Parameters:

binding - the variable binding

Returns:

true if this expression is the variable binding (for example a ForExpression or LetExpression) or if it is a FLWOR expression that binds the variable in one of its clauses.

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:

unordered in class Expression

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

getCost

public double getCost()

Return the estimated cost of evaluating an expression. This is a very crude measure based on the syntactic form of the expression (we have no knowledge of data values). We take the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one), and we assume that a sequence has length 5. The resulting estimates may be used, for example, to reorder the predicates in a filter expression so cheaper predicates are evaluated first.

Overrides:

getCost in class Expression

Returns:

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

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 java.lang.String getVariableName()

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

Returns:

the lexical QName of the range variable. For system allocated variables, the conventional namespace prefix "zz" is used.

getVariableEQName

public java.lang.String getVariableEQName()

Get the name of the range variable as a Name or EQName.

Returns:

the name of the range variable. For system allocated variables, the namespace "http://ns.saxonica.com/anonymous-var" is used. For names in no namespace, the local name alone is used

refineTypeInformation

public void refineTypeInformation(ItemType type,
                                  int cardinality,
                                  GroundedValue<?> constantValue,
                                  int properties,
                                  Assignation currentExpression)
                           throws XPathException

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

currentExpression - the expression that binds the variable

Throws:

XPathException

addReference

public void addReference(VariableReference ref,
                         boolean isLoopingReference)

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

Specified by:

addReference in interface Binding

Parameters:

ref - the variable reference

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.

removeDeadReferences

protected boolean removeDeadReferences()

Remove dead references from the reference list of the variable; at the same time, check whether any of the variable references is in a loop, and return true if so. References are considered dead if they do not have this Binding as an ancestor in the expression tree; this typically occurs because they are in a part of the tree that has been rewritten or removed.

Returns:

true if any of the references in the reference list occurs within a looping construct.

verifyReferences

protected void verifyReferences()

This method recomputes the reference list by scanning the subtree rooted at this variable binding. If the scan proves expensive, or if more than two references are found, or if a looping reference is found, then the scan is abandoned. On completion the reference list for the variable is either accurate, or is null.

rebuildReferenceList

public void rebuildReferenceList(boolean force)

Rebuild the reference list to guide subsequent optimization.

Parameters:

force - if true, the search is exhaustive. If false, the search (and therefore the attempt to inline variables) is abandoned after a while to avoid excessive cost. This happens when a stylesheet contains very large templates or functions.

isIndexedVariable

public boolean isIndexedVariable()

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

Specified by:

isIndexedVariable in interface LocalBinding

Returns:

true if the variable should be indexable

replaceVariable

public boolean replaceVariable(Expression seq)

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

Parameters:

seq - the expression

Returns:

true if the variable was successfully inlined. (Returns false, for example, if a variable reference occurs inside a try/catch, which inhibits inlining).

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)

Specified by:

setIndexedVariable in interface LocalBinding