Package net.sf.saxon.expr
Class LookupAllExpression
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.UnaryExpression
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- net.sf.saxon.expr.LookupAllExpression
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- All Implemented Interfaces:
ExportAgent,Locatable,IdentityComparable,Traceable
public class LookupAllExpression extends UnaryExpression
A lookup expression is an expression of the form A?*, where A must be a map or an array
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Field Summary
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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 Constructor Description LookupAllExpression(Expression base)Constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description intcomputeCardinality()Determine the static cardinality of the expressionintcomputeHashCode()get HashCode for comparing two expressionsLookupAllExpressioncopy(RebindingMap rebindings)Copy an expression.booleanequals(java.lang.Object other)Is this expression the same as another expression?voidexport(ExpressionPresenter destination)Diagnostic print of expression structure.doublegetCost()Return the estimated cost of evaluating an expression.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().ItemTypegetItemType()Determine the data type of the items returned by this expressionprotected OperandRolegetOperandRole()Get the usage (in terms of streamability analysis) of the single operandUTypegetStaticUType(UType contextItemType)Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.SequenceIteratoriterate(XPathContext context)Iterate the lookup-expression in a given contextExpressionoptimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)Perform optimisation of an expression and its subexpressions.java.lang.StringtoShortString()Produce a short string identifying the expression for use in error messagesjava.lang.StringtoString()The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.ExpressiontypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Type-check the expression-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeSpecialProperties, displayOperator, emitExtraAttributes, getBaseExpression, getOperand, operands, setBaseExpression
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getDependencies, getEvaluationMethod, getExpressionName, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Detail
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LookupAllExpression
public LookupAllExpression(Expression base)
Constructor- Parameters:
base- The left hand operand (which must always select a sequence of maps or arrays).
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Method Detail
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getOperandRole
protected OperandRole getOperandRole()
Description copied from class:UnaryExpressionGet the usage (in terms of streamability analysis) of the single operand- Specified by:
getOperandRolein classUnaryExpression- Returns:
- the operand usage
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getItemType
public final ItemType getItemType()
Determine the data type of the items returned by this expression- Overrides:
getItemTypein classUnaryExpression- Returns:
- the type of the step
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getStaticUType
public UType getStaticUType(UType contextItemType)
Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.- Overrides:
getStaticUTypein classExpression- Parameters:
contextItemType- The type of the context item (not used)- Returns:
- the static item type of the expression according to the XSLT 3.0 defined rules
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Type-check the expression- Overrides:
typeCheckin classUnaryExpression- Parameters:
visitor- an expression visitorcontextInfo- Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException- if an error is discovered during this phase (typically a type error)
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optimize
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException
Description copied from class:UnaryExpressionPerform optimisation of an expression and its subexpressions.This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
- Overrides:
optimizein classUnaryExpression- Parameters:
visitor- an expression visitorcontextItemType- 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- if an error is discovered during this phase (typically a type error)
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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:
getCostin classExpression- Returns:
- a rough estimate of the cost of evaluation
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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 directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.- Specified by:
getImplementationMethodin classExpression- Returns:
- the implementation method, for example
Expression.ITERATE_METHODorExpression.EVALUATE_METHODorExpression.PROCESS_METHOD
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copy
public LookupAllExpression copy(RebindingMap rebindings)
Copy an expression. This makes a deep copy.- Specified by:
copyin classExpression- Parameters:
rebindings- variables that need to be re-bound.- Returns:
- the copy of the original expression
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computeCardinality
public int computeCardinality()
Determine the static cardinality of the expression- Overrides:
computeCardinalityin classUnaryExpression- Returns:
- the computed cardinality, as one of the values
StaticProperty.ALLOWS_ZERO_OR_ONE,StaticProperty.EXACTLY_ONE,StaticProperty.ALLOWS_ONE_OR_MORE,StaticProperty.ALLOWS_ZERO_OR_MORE. May also returnStaticProperty.ALLOWS_ZEROif the result is known to be an empty sequence, orStaticProperty.ALLOWS_MANYif if is known to return a sequence of length two or more.
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equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equalsin classUnaryExpression- Parameters:
other- the other operand; the result is false if this is not an Expression- Returns:
- true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
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computeHashCode
public int computeHashCode()
get HashCode for comparing two expressions- Overrides:
computeHashCodein classUnaryExpression- Returns:
- a computed hash code
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Iterate the lookup-expression in a given context- Overrides:
iteratein classExpression- Parameters:
context- the evaluation context- 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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export
public void export(ExpressionPresenter destination) throws XPathException
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
exportin interfaceExportAgent- Overrides:
exportin classUnaryExpression- Parameters:
destination- the expression presenter used to display the structure- Throws:
XPathException- if the export fails, for example if an expression is found that won't work in the target environment.
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toString
public java.lang.String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax- Overrides:
toStringin classUnaryExpression- Returns:
- a representation of the expression as a string
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toShortString
public java.lang.String toShortString()
Description copied from class:ExpressionProduce a short string identifying the expression for use in error messages- Overrides:
toShortStringin classUnaryExpression- Returns:
- a short string, sufficient to identify the expression
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