net.sf.saxon.expr
Class AxisExpression
- EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator
public final class AxisExpression
An AxisExpression is always obtained by simplifying a PathExpression.
It represents a PathExpression that starts at the context 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 Reverser.
addToPathMap , adoptChildExpression , checkPermittedContents , computeCardinality , computeDependencies , computeSpecialProperties , computeStaticProperties , copy , display , doPromotion , dynamicError , effectiveBooleanValue , evaluateAsString , evaluateItem , explain , explain , findParentOf , getCardinality , getColumnNumber , getConstructType , getContainer , getDependencies , getExecutable , getHostLanguage , getImplementationMethod , getInstructionInfo , getIntrinsicDependencies , getItemType , getLineNumber , getLocationId , getLocationProvider , getPublicId , getSlotsUsed , getSpecialProperties , getSystemId , hasLoopingSubexpression , implementsStaticTypeCheck , iterate , iterateEvents , iterateSubExpressions , markTailFunctionCalls , optimize , process , promote , replaceSubExpression , resetLocalStaticProperties , setContainer , setFiltered , setFlattened , setLocationId , simplify , staticTypeCheck , suppressValidation , toString , typeCheck , typeError |
AxisExpression
public AxisExpression(byte axis,
NodeTest nodeTest)
Constructor
axis
- The axis to be used in this AxisExpression: relevant constants are defined
in class net.sf.saxon.om.Axis.nodeTest
- The conditions to be satisfied by selected nodes. May be null,
indicating that any node on the axis is acceptable
addToPathMap
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited
by an expression in a source tree.
- addToPathMap in interface Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-
- the pathMapNode representing the focus established by this expression, in the case where this
expression is the first operand of a path expression or filter expression
computeCardinality
public final int computeCardinality()
Specify that the expression returns a singleton
- computeCardinality in interface Expression
computeSpecialProperties
public int computeSpecialProperties()
Get the static properties of this expression (other than its type). The result is
bit-signficant. These properties are used for optimizations. In general, if
property bit is set, it is true, but if it is unset, the value is unknown.
- computeSpecialProperties in interface Expression
copy
public Expression copy()
Copy an expression. This makes a deep copy.
- copy in interface Expression
- the copy of the original expression
equals
public boolean equals(Object other)
Is this expression the same as another expression?
explain
public void explain(ExpressionPresenter destination)
Diagnostic print of expression structure. The abstract expression tree
is written to the supplied output destination.
- explain in interface Expression
getAxis
public byte getAxis()
Get the axis
getContextItemType
public ItemType getContextItemType()
Get the static type of the context item for this AxisExpression. May be null if not known.
- the statically-inferred type, or null if not known
getIntrinsicDependencies
public int getIntrinsicDependencies()
Determine which aspects of the context the expression depends on. The result is
a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and
XPathContext.CURRENT_NODE
- getIntrinsicDependencies in interface Expression
getItemType
public final ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression
- getItemType in interface Expression
th
- the type hierarchy cache
- Type.NODE or a subtype, based on the NodeTest in the axis step, plus
information about the content type if this is known from schema analysis
getNodeTest
public NodeTest getNodeTest()
Get the NodeTest. Returns null if the AxisExpression can return any node.
- the node test, or null if all nodes are returned
hashCode
public int hashCode()
get HashCode for comparing two expressions
iterate
public SequenceIterator iterate(Item origin)
throws XPathException
Iterate the axis from a given starting node, without regard to context
origin
- the starting node
- the iterator over the axis
optimize
public Expression optimize(ExpressionVisitor visitor,
ItemType contextItemType)
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.
- optimize in interface 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
- the original expression, rewritten if appropriate to optimize execution
toString
public String toString()
Represent the expression as a string for diagnostics
- toString in interface Expression
toString
public String toString(NamePool pool)
Represent the expression as a string for diagnostics
pool
- the name pool, used for expanding names in the node test
- a string representation of the expression