public class SlashExpression extends Expression implements ContextMappingFunction
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
Constructor and Description |
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SlashExpression(Expression start,
Expression step)
Constructor
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Modifier and Type | Method and Description |
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int |
computeCardinality()
Determine the static cardinality of the expression
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int |
computeDependencies()
Determine which aspects of the context the expression depends on.
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int |
computeSpecialProperties()
Get the static properties of this expression (other than its type).
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Expression |
copy()
Copy an expression.
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boolean |
equals(java.lang.Object other)
Is this expression the same as another expression?
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void |
explain(ExpressionPresenter destination)
Diagnostic print of expression structure.
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ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this exprssion
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Expression |
getStartExpression()
Get the start expression (the left-hand operand)
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Expression |
getStepExpression()
Get the step expression (the right-hand operand)
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int |
hashCode()
get HashCode for comparing two expressions
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boolean |
hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether
the evaluation of the parent expression causes the child expression to be
evaluated repeatedly
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boolean |
isHybrid()
Determine whether this expression is capable (as far as static analysis is concerned)
of returning a mixture of nodes and atomic values.
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SequenceIterator |
iterate(XPathContext context)
Iterate the path-expression in a given context
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java.util.Iterator |
iterateSubExpressions()
Get the immediate subexpressions of this expression
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static SlashExpression |
makeSlashExpression(Expression start,
Expression step,
TypeHierarchy th)
Static factory method, allowing early instantiation of a subclass if the type of the step expression
is already known
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SequenceIterator |
map(XPathContext context)
Mapping function, from a node returned by the start iteration, to a sequence
returned by the child.
|
Expression |
optimize(ExpressionVisitor visitor,
ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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Expression |
promote(PromotionOffer offer)
Promote this expression if possible
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protected Expression |
promoteFocusIndependentSubexpressions(ExpressionVisitor visitor,
ItemType contextItemType)
If any subexpressions within the step are not dependent on the focus,
and if they are not "creative" expressions (expressions that can create new nodes), then
promote them: this causes them to be evaluated once, outside the path expression
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boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression
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protected void |
setStartExpression(Expression start2) |
protected void |
setStepExpression(Expression step2) |
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression
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Expression |
typeCheck(ExpressionVisitor visitor,
ItemType contextItemType)
Type-check the expression
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addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
public SlashExpression(Expression start, Expression step)
start
- The left hand operand (which must always select a sequence of nodes).step
- The step to be followed from each node in the start expression to yield a new
sequence; this may return either nodes or atomic values (but not a mixture of the two)protected void setStartExpression(Expression start2)
protected void setStepExpression(Expression step2)
public static SlashExpression makeSlashExpression(Expression start, Expression step, TypeHierarchy th)
public Expression getStartExpression()
public Expression getStepExpression()
public boolean isHybrid()
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
- the expression visitorXPathException
- if an error is discovered during expression
rewritingpublic final ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cachepublic Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
typeCheck
in class Expression
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 to
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Expression
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.
optimize
in class Expression
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 to
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)protected Expression promoteFocusIndependentSubexpressions(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
visitor
- the expression visitorcontextItemType
- the type of the context item for evaluating the start expressionXPathException
public Expression promote(PromotionOffer offer) throws XPathException
promote
in class Expression
offer
- details of the offer, for example the offer to move
expressions that don't depend on the context to an outer level in
the containing expressionXPathException
- if any error is detectedpublic java.util.Iterator iterateSubExpressions()
iterateSubExpressions
in class Expression
public boolean hasLoopingSubexpression(Expression child)
hasLoopingSubexpression
in class Expression
child
- the immediate subexpressionpublic boolean replaceSubExpression(Expression original, Expression replacement)
replaceSubExpression
in class Expression
original
- the original subexpressionreplacement
- the replacement subexpressionpublic int computeDependencies()
computeDependencies
in class Expression
public Expression copy()
copy
in class Expression
public int computeSpecialProperties()
computeSpecialProperties
in class Expression
public int computeCardinality()
computeCardinality
in class Expression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
public boolean equals(java.lang.Object other)
equals
in class java.lang.Object
public int hashCode()
hashCode
in class java.lang.Object
public SequenceIterator iterate(XPathContext context) throws XPathException
iterate
in interface SequenceIterable
iterate
in class Expression
context
- the evaluation contextXPathException
- if any dynamic error occurs evaluating the
expressionpublic final SequenceIterator map(XPathContext context) throws XPathException
map
in interface ContextMappingFunction
context
- The processing context. The item to be mapped is the context item identified
from this context: the values of position() and last() also relate to the set of items being mappedXPathException
public void explain(ExpressionPresenter destination)
explain
in class Expression
destination
- the expression presenter used to display the structure