Package net.sf.saxon.expr.instruct
Class SequenceInstr
- 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.instruct.SequenceInstr
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- All Implemented Interfaces:
ExportAgent,Locatable,IdentityComparable,Traceable
public class SequenceInstr extends UnaryExpression
A compiled xsl:sequence instruction. Used only when strict streamability analysis is required; the instruction differs from its operand only by being marked as an instruction, which is sometimes relevant for streamability analysis. Used for xsl:sequence and also for xsl:map and xsl:map-entry; and also to wrap expressions in text value templates.
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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 SequenceInstr(Expression base)Create the instruction
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Expressioncopy(RebindingMap rebindings)Copy an expression.voidexport(ExpressionPresenter out)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().protected OperandRolegetOperandRole()Get the usage (in terms of streamability analysis) of the single operandjava.lang.StringgetStreamerName()Get the (partial) name of a class that supports streaming of this kind of expressionbooleanisInstruction()Ask whether this expression is an instruction.SequenceIteratoriterate(XPathContext context)Return an Iterator to iterate over the values of a sequence.Expressionoptimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Perform optimisation of an expression and its subexpressions.voidprocess(Outputter output, XPathContext context)Process the instruction, without returning any tail callsExpressiontypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)Type-check the expression.-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeCardinality, computeHashCode, computeSpecialProperties, displayOperator, emitExtraAttributes, equals, getBaseExpression, getItemType, getOperand, operands, setBaseExpression, toShortString, toString
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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, 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, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, 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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SequenceInstr
public SequenceInstr(Expression base)
Create the instruction
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Method Detail
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isInstruction
public boolean isInstruction()
Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs.- Overrides:
isInstructionin classExpression- Returns:
- true if this construct originates as an XSLT instruction
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getOperandRole
protected OperandRole getOperandRole()
Get the usage (in terms of streamability analysis) of the single operand- Specified by:
getOperandRolein classUnaryExpression- Returns:
- the operand usage
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
Type-check the expression. Default implementation for unary operators that accept any kind of operand- 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
Perform 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 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)
Description copied from class:ExpressionCopy an expression. This makes a deep copy.- Specified by:
copyin classExpression- Parameters:
rebindings- a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.- Returns:
- the copy of the original expression
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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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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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process
public void process(Outputter output, XPathContext context) throws XPathException
Process the instruction, without returning any tail calls- Overrides:
processin classExpression- Parameters:
output- the destination for the resultcontext- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException- if a dynamic error occurs
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.- Overrides:
iteratein classExpression- Parameters:
context- supplies the context for evaluation- 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 out) throws XPathException
Description copied from class:UnaryExpressionDiagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
exportin interfaceExportAgent- Overrides:
exportin classUnaryExpression- Parameters:
out- 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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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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