Package net.sf.saxon.expr
Class SimpleStepExpression
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.SlashExpression
net.sf.saxon.expr.SimpleStepExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,ContextMappingFunction<Item>
,ContextSwitchingExpression
,InstructionInfo
,Locator
An SimpleStepExpression is a special case of a SlashExpression in which the
start expression selects a single item (or nothing), and the step expression is
a simple AxisExpression. This is designed to avoid the costs of creating a new
dynamic context for expressions (common in XQuery) such as
for $b in EXPR return $b/title
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.SlashExpression
start, step
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptioncopy()
Copy an expression.iterate
(XPathContext context) Evaluate the expression, returning an iterator over the resultoptimize
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.typeCheck
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.SlashExpression
addToPathMap, computeCardinality, computeDependencies, computeSpecialProperties, equals, explain, getControlledExpression, getControllingExpression, getFirstStep, getIntegerBounds, getItemType, getLastStep, getLeadingSteps, getRemainingSteps, getStep, hashCode, hasLoopingSubexpression, isAbsolute, iterateSameFocusSubExpressions, iterateSubExpressions, map, promote, promoteFocusIndependentSubexpressions, replaceSubExpression, setStartExpression, setStepExpression, simplify, toString, tryToMakeAbsolute
Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Details
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SimpleStepExpression
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Method Details
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Description copied from class:SlashExpression
Type-check the expression- Overrides:
typeCheck
in classSlashExpression
- 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 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, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Description copied from class:Expression
Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.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:
optimize
in classSlashExpression
- 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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copy
Copy an expression. This makes a deep copy.- Overrides:
copy
in classSlashExpression
- Returns:
- the copy of the original expression
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iterate
Evaluate the expression, returning an iterator over the result- Overrides:
iterate
in classSlashExpression
- 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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