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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.SlashExpression
public class SlashExpression
A slash expression is any expression using the binary slash operator "/". The parser initially generates a slash expression for all occurrences of the binary "/" operator. Subsequently, as a result of type inferencing, the majority of slash expressions will be rewritten as instances of PathExpression (returning nodes) or ForEach instructions (when they return atomic values). However, in the rare case where it is not possible to determine statically whether the rh operand returns nodes or atomic values, instances of this class may need to be interpreted directly at run time.
Field Summary |
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Fields inherited from class net.sf.saxon.expr.Expression |
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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 |
Constructor Summary | |
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SlashExpression(Expression start,
Expression step)
Constructor |
Method Summary | |
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PathMap.PathMapNodeSet |
addToPathMap(PathMap pathMap,
PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. |
int |
computeCardinality()
Determine the static cardinality of the expression |
int |
computeDependencies()
Determine which aspects of the context the expression depends on. |
int |
computeSpecialProperties()
Get the static properties of this expression (other than its type). |
Expression |
copy()
Copy an expression. |
boolean |
equals(Object other)
Is this expression the same as another expression? |
void |
explain(ExpressionPresenter destination)
Diagnostic print of expression structure. |
Expression |
getControlledExpression()
Get the step expression (the right-hand operand) |
Expression |
getControllingExpression()
Get the start expression (the left-hand operand) |
Expression |
getFirstStep()
Get the first step in this expression. |
IntegerValue[] |
getIntegerBounds()
For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this exprssion |
Expression |
getLastStep()
Get the last step of the path expression |
Expression |
getLeadingSteps()
Get a path expression consisting of all steps except the last |
Expression |
getRemainingSteps()
Get all steps after the first. |
Expression |
getStep()
Get step of the path expression |
int |
hashCode()
get HashCode for comparing two expressions |
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 |
boolean |
isAbsolute(TypeHierarchy th)
Test whether a path expression is an absolute path - that is, a path whose first step selects a document node |
SequenceIterator<? extends Item> |
iterate(XPathContext context)
Iterate the path-expression in a given context |
Iterator<Expression> |
iterateSameFocusSubExpressions()
Get the immediate sub-expressions of this expression that are evaluated with the same focus (context item, position, and size) as the parent expression. |
Iterator<Expression> |
iterateSubExpressions()
Get the immediate subexpressions of this expression |
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,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
Expression |
promote(PromotionOffer offer,
Expression parent)
Promote this expression if possible |
protected Expression |
promoteFocusIndependentSubexpressions(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType 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 |
boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression |
void |
setStartExpression(Expression start2)
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void |
setStepExpression(Expression step2)
|
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression |
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. |
SlashExpression |
tryToMakeAbsolute(TypeHierarchy th)
Test whether a path expression is an absolute path - that is, a path whose first step selects a document node; if not, see if it can be converted to an absolute path. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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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)Method Detail |
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public void setStartExpression(Expression start2)
public void setStepExpression(Expression step2)
public Expression getControllingExpression()
getControllingExpression
in interface ContextSwitchingExpression
public Expression getControlledExpression()
getControlledExpression
in interface ContextSwitchingExpression
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
- the expression visitor
XPathException
- if an error is discovered during expression
rewritingpublic final ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public IntegerValue[] getIntegerBounds()
getIntegerBounds
in class Expression
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType 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, ExpressionVisitor.ContextItemType 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)public SlashExpression tryToMakeAbsolute(TypeHierarchy th)
th
- the type hierarchy cache
protected Expression promoteFocusIndependentSubexpressions(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
visitor
- the expression visitorcontextItemType
- the type of the context item for evaluating the start expression
XPathException
- if a static error is detectedpublic Expression promote(PromotionOffer offer, Expression parent) 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 expressionparent
- the containing expression in the expression tree
XPathException
- if any error is detectedpublic Iterator<Expression> iterateSubExpressions()
iterateSubExpressions
in class Expression
public Iterator<Expression> iterateSameFocusSubExpressions()
iterateSameFocusSubExpressions
in class Expression
public boolean hasLoopingSubexpression(Expression child)
hasLoopingSubexpression
in class Expression
child
- the immediate subexpression
public boolean replaceSubExpression(Expression original, Expression replacement)
replaceSubExpression
in class Expression
original
- the original subexpressionreplacement
- the replacement subexpression
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
addToPathMap
in class Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-
public 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(Object other)
equals
in class Object
public int hashCode()
hashCode
in class Object
public SequenceIterator<? extends Item> iterate(XPathContext context) throws XPathException
iterate
in class Expression
context
- the evaluation context
XPathException
- if any dynamic error occurs evaluating the
expressionpublic SequenceIterator map(XPathContext context) throws XPathException
map
in interface ContextMappingFunction<Item>
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 mapped
XPathException
- if a dynamic error is detectedpublic void explain(ExpressionPresenter destination)
explain
in class Expression
destination
- the expression presenter used to display the structurepublic String toString()
toString
in class Expression
public Expression getFirstStep()
public Expression getStep()
public Expression getRemainingSteps()
public Expression getLastStep()
public Expression getLeadingSteps()
public boolean isAbsolute(TypeHierarchy th)
th
- the type hierarchy cache
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