Class Assignation
- All Implemented Interfaces:
Binding
,ExportAgent
,LocalBinding
,Locatable
,IdentityComparable
,Traceable
- Direct Known Subclasses:
ForExpression
,LetExpression
,QuantifiedExpression
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Field Summary
FieldsModifier and TypeFieldDescriptionprotected boolean
protected boolean
protected List
<VariableReference> protected SequenceType
protected int
protected StructuredQName
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
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
addReference
(VariableReference ref, boolean isLoopingReference) Register a variable reference that refers to the variable bound in this expressionaddToPathMap
(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.void
Check to ensure that this expression does not contain any inappropriate updating subexpressions.int
Compute the dependencies of an expression, as the union of the dependencies of its sub-expressions.evaluateVariable
(XPathContext context) Get the value of the range variableGet the action expressiondouble
getCost()
Return the estimated cost of evaluating an expression.If the variable is bound to an integer, get the minimum and maximum possible values.int
If this is a local variable held on the local stack frame, return the corresponding slot number.int
Get the (nominal) count of the number of references to this variableGet a name identifying the object of the expression, for example a function name, template name, variable name, key name, element name, etc.int
Get the number of slots required.Get the declared type of the variableGet the "sequence" expression - the one to which the variable is boundGet the name of the range variable as a Name or EQName.Get the display name of the range variable, for diagnostics onlyGet the name of the variableboolean
hasVariableBinding
(Binding binding) Ask whether this expression is, or contains, the binding of a given variablefinal boolean
Test whether it is permitted to assign to the variable using the saxon:assign extension element.final boolean
isGlobal()
Indicate whether the binding is local or global.boolean
Test whether the variable bound by this let expression should be indexableboolean
Determine whether this is an updating expression as defined in the XQuery update specificationoperands()
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
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
Replace all references to the variable bound by this let expression, that occur within the action expression, with the given expressionvoid
setAction
(Expression action) Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expressionvoid
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 variablevoid
setSequence
(Expression sequence) Set the "sequence" expression - the one to which the variable is boundvoid
setSlotNumber
(int nr) Set the slot number for the range variablevoid
setVariableQName
(StructuredQName variableName) Set the name of the variablevoid
suppressValidation
(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.unordered
(boolean retainAllNodes, boolean forStreaming) Replace this expression by a simpler expression that delivers the results without regard to order.protected void
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, dispatchTailCall, dynamicError, effectiveBooleanValue, equals, evaluateAsString, evaluateItem, explain, export, getCardinality, getConfiguration, getDependencies, getElaborator, getEvaluationMethod, getExpressionName, getExtraProperty, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getItemType, getLocalRetainedStaticContext, getLocation, getNetCost, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isVacuousExpression, iterate, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, toPattern, toShortString, toString, typeCheck, typeCheckChildren, typeError, verifyParentPointers, withLocation
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Field Details
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Constructor Details
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Method Details
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getSequenceOp
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getActionOp
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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.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 classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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setRequiredType
Set the required type (declared type) of the variable- Parameters:
requiredType
- the required type
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setVariableQName
Set the name of the variable- Parameters:
variableName
- the name of the variable
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getVariableQName
Get the name of the variable- Specified by:
getVariableQName
in interfaceBinding
- Returns:
- the variable name, as a QName
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getObjectName
Description copied from interface:Traceable
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 interfaceTraceable
- Overrides:
getObjectName
in classExpression
- Returns:
- the QName of the object declared or manipulated by this instruction or expression
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getRequiredType
Get the declared type of the variable- Specified by:
getRequiredType
in interfaceBinding
- Returns:
- the declared type
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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 interfaceBinding
- 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
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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 interfaceLocalBinding
- Returns:
- the slot number on the local stack frame
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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 classExpression
- Returns:
- the dependencies, as a bit-mask
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evaluateVariable
Get the value of the range variable- Specified by:
evaluateVariable
in interfaceBinding
- Parameters:
context
- the XPath dynamic evaluation context- Returns:
- the result of evaluating the variable
- Throws:
XPathException
- if an error occurs while evaluating the variable
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setAction
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.
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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. -
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 interfaceBinding
- Returns:
- true if the binding is assignable
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checkForUpdatingSubexpressions
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 classExpression
- Throws:
XPathException
- if the expression has a non-permitted updateing subexpression
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isUpdatingExpression
public boolean isUpdatingExpression()Determine whether this is an updating expression as defined in the XQuery update specification- Overrides:
isUpdatingExpression
in classExpression
- Returns:
- true if this is an updating expression
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getAction
Get the action expression- Returns:
- the action expression (introduced by "return" or "satisfies")
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setSequence
Set the "sequence" expression - the one to which the variable is bound- Parameters:
sequence
- the expression to which the variable is bound
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getSequence
Get the "sequence" expression - the one to which the variable is bound- Returns:
- the expression to which the variable is bound
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setSlotNumber
public void setSlotNumber(int nr) Set the slot number for the range variable- Parameters:
nr
- the slot number to be used
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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.- Returns:
- the number of slots required
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hasVariableBinding
Description copied from class:Expression
Ask whether this expression is, or contains, the binding of a given variable- Overrides:
hasVariableBinding
in classExpression
- 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.
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unordered
Replace this expression by a simpler expression that delivers the results without regard to order.- Overrides:
unordered
in classExpression
- 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
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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 classExpression
- Returns:
- the estimated cost
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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 classExpression
- Parameters:
validationMode
- the kind of validation being performed on the parent expression
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addToPathMap
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 classExpression
- Parameters:
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- 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.
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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.
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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
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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 boundcardinality
- the inferred cardinality of the expression to which the variable is boundconstantValue
- 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 boundcurrentExpression
- the expression that binds the variable- Throws:
XPathException
- if things go wrong
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addReference
Register a variable reference that refers to the variable bound in this expression- Specified by:
addReference
in interfaceBinding
- Parameters:
ref
- the variable referenceisLoopingReference
- - true if the reference occurs within a loop, such as the predicate of a filter expression
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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.
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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.
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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.
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isIndexedVariable
public boolean isIndexedVariable()Test whether the variable bound by this let expression should be indexable- Specified by:
isIndexedVariable
in interfaceLocalBinding
- Returns:
- true if the variable should be indexable
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replaceVariable
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).
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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 interfaceLocalBinding
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