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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.AxisExpression
public final class AxisExpression
An AxisExpression is always obtained by simplifying a PathExpression. It represents a PathExpression that starts either at the context node or at some other singleton node, and uses a simple node-test with no filters. For example "*", "title", "./item", "@*", or "ancestor::chapter*".
An AxisExpression delivers nodes in axis order (not in document order). To get nodes in document order, in the case of a reverse axis, the expression should be wrapped in a call on reverse().
Since 9.4, an axis expression does not necessarily select starting from the context item. This allows an expression such as $x/abcd (very common in XQuery FLWOR expressions) to be computed without creating a new context.
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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AxisExpression(byte axis,
NodeTest nodeTest)
Constructor for an AxisExpression whose origin is the context item |
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 cardinality of the result of this expression |
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. |
byte |
getAxis()
Get the axis |
ItemType |
getContextItemType()
Get the static type of the context item for this AxisExpression. |
String |
getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user. |
int |
getIntrinsicDependencies()
Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression |
NodeTest |
getNodeTest()
Get the NodeTest. |
int |
hashCode()
get HashCode for comparing two expressions |
boolean |
isContextPossiblyUndefined()
Ask whether there is a possibility that the context item will be undefined |
boolean |
isSubtreeExpression()
Determine whether the expression can be evaluated without reference to the part of the context document outside the subtree rooted at the context node. |
SequenceIterator |
iterate(Item origin)
Iterate the axis from a given starting node, without regard to context |
AxisIterator<? extends NodeInfo> |
iterate(XPathContext context)
Evaluate the path-expression in a given context to return a NodeSet |
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression |
String |
toString()
Represent the expression as a string for diagnostics |
String |
toString(NamePool pool)
Represent the expression as a string for diagnostics |
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 AxisExpression(byte axis, NodeTest nodeTest)
axis
- The axis to be used in this AxisExpression: relevant constants are defined
in class Axis
.nodeTest
- The conditions to be satisfied by selected nodes. May be null,
indicating that any node on the axis is acceptableAxis
Method Detail |
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public String getExpressionName()
getExpressionName
in class Expression
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
- an expression visitor
XPathException
- if an error is discovered during expression
rewritingpublic 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 ItemType getContextItemType()
public boolean equals(Object other)
equals
in class Object
public int hashCode()
hashCode
in class Object
public Expression copy()
copy
in class Expression
public int computeSpecialProperties()
computeSpecialProperties
in class Expression
public final ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public int getIntrinsicDependencies()
getIntrinsicDependencies
in class Expression
public final 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 isSubtreeExpression()
isSubtreeExpression
in class Expression
public byte getAxis()
Axis.CHILD
public NodeTest getNodeTest()
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
addToPathMap
in class Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-
public boolean isContextPossiblyUndefined()
public AxisIterator<? extends NodeInfo> iterate(XPathContext context) throws XPathException
iterate
in class Expression
context
- the evaluation context
XPathException
- if any dynamic error occurs evaluating the
expressionpublic SequenceIterator iterate(Item origin) throws XPathException
origin
- the starting node
XPathException
public void explain(ExpressionPresenter destination)
explain
in class Expression
destination
- the expression presenter used to display the structurepublic String toString()
toString
in class Expression
public String toString(NamePool pool)
pool
- the name pool, used for expanding names in the node test
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