Class SubscriptExpression
- 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.SingleItemFilter
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- net.sf.saxon.expr.SubscriptExpression
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- All Implemented Interfaces:
ExportAgent,Locatable,IdentityComparable,Traceable
public class SubscriptExpression extends SingleItemFilter
A SubscriptExpression represents a FilterExpression of the form EXPR[n] where n is known to be singleton numeric and to be independent of the focus; it does not need to be constant
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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 SubscriptExpression(Expression base, Expression subscript)Construct a SubscriptExpression
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description intcomputeCardinality()Get the static cardinality: this implementation is appropriate for [1] and [last()] which will always return something if the input is non-emptyintcomputeHashCode()get HashCode for comparing two expressions.Expressioncopy(RebindingMap rebindings)Copy an expression.booleanequals(java.lang.Object other)Compare two expressions to see if they are equalItemevaluateItem(XPathContext context)Evaluate an expression as a single item.voidexport(ExpressionPresenter destination)Diagnostic print of expression structure.java.lang.StringgetExpressionName()Get a name identifying the kind of expression, in terms meaningful to a user.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().java.lang.StringgetStreamerName()Get the (partial) name of a class that supports streaming of this kind of expressionExpressiongetSubscript()ExpressiongetSubscriptExpression()Get the subscript expressionjava.lang.Iterable<Operand>operands()Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.Expressionoptimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Perform optimisation of an expression and its subexpressions.voidsetSubscript(Expression subscript)java.lang.StringtoShortString()The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.java.lang.StringtoString()The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.ExpressiontypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Type-check the expression.-
Methods inherited from class net.sf.saxon.expr.SingleItemFilter
getOperandRole
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Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeSpecialProperties, displayOperator, emitExtraAttributes, getBaseExpression, getItemType, getOperand, 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, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, 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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SubscriptExpression
public SubscriptExpression(Expression base, Expression subscript)
Construct a SubscriptExpression- Parameters:
base- the expression to be filteredsubscript- the positional subscript filter
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Method Detail
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getSubscript
public Expression getSubscript()
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setSubscript
public void setSubscript(Expression subscript)
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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 contextInfo) throws XPathException
Description copied from class:SingleItemFilterPerform 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 classSingleItemFilter- Parameters:
visitor- an expresion visitorcontextInfo- 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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copy
public Expression 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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operands
public java.lang.Iterable<Operand> operands()
Description copied from class:ExpressionGet 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:
operandsin classUnaryExpression- Returns:
- an iterator containing the sub-expressions of this expression
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getSubscriptExpression
public Expression getSubscriptExpression()
Get the subscript expression- Returns:
- the expression used to compute the one-based start offset
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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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equals
public boolean equals(java.lang.Object other)
Compare two expressions to see if they are equal- Overrides:
equalsin classUnaryExpression- Parameters:
other- the other expression- Returns:
- true if the expressions are equivalent
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computeHashCode
public int computeHashCode()
Description copied from class:UnaryExpressionget HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.- Overrides:
computeHashCodein classUnaryExpression- Returns:
- a computed hash code
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computeCardinality
public int computeCardinality()
Get the static cardinality: this implementation is appropriate for [1] and [last()] which will always return something if the input is non-empty- Overrides:
computeCardinalityin classSingleItemFilter- 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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getStreamerName
public java.lang.String getStreamerName()
Get the (partial) name of a class that supports streaming of this kind of expression- Overrides:
getStreamerNamein classExpression- Returns:
- the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Description copied from class:ExpressionEvaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.- Overrides:
evaluateItemin classExpression- Parameters:
context- The context in which the expression is to be evaluated- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException- if any dynamic error occurs evaluating the expression
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionNamein classExpression- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying 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.
For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression.
- Overrides:
toStringin classUnaryExpression- Returns:
- a representation of the expression as a string
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toShortString
public java.lang.String toShortString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.
For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression.
- Overrides:
toShortStringin classUnaryExpression- Returns:
- a representation of the expression as a string
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