AxisExpression

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.AxisExpression

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
public final class AxisExpression
extends Expression
```
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 call on reverse().

See Also:

Serialized Form

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties

Constructor Summary

Constructors
Constructor Description

AxisExpression(byte axis, NodeTest nodeTest)
Constructor

Constructors
Constructor	Description
`AxisExpression(byte axis, NodeTest nodeTest)`	Constructor

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`PathMap.PathMapNodeSet`	`addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)`	Add a representation of this expression to a PathMap.
`int`	`computeCardinality()`	Specify that the expression returns a singleton
`int`	`computeSpecialProperties()`	Get the static properties of this expression (other than its type).
`Expression`	`copy()`	Copy an expression.
`boolean`	`equals(java.lang.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.
`int`	`getIntrinsicDependencies()`	Determine which aspects of the context the expression depends on.
`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
`SequenceIterator`	`iterate(XPathContext context)`	Evaluate the path-expression in a given context to return a NodeSet
`SequenceIterator`	`iterate(Item origin)`	Iterate the axis from a given starting node, without regard to context
`Expression`	`optimize(ExpressionVisitor visitor, ItemType contextItemType)`	Perform optimisation of an expression and its subexpressions.
`Expression`	`simplify(ExpressionVisitor visitor)`	Simplify an expression
`java.lang.String`	`toString()`	Represent the expression as a string for diagnostics
`java.lang.String`	`toString(NamePool pool)`	Represent the expression as a string for diagnostics
`Expression`	`typeCheck(ExpressionVisitor visitor, ItemType contextItemType)`	Type-check the expression

Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, iterateSubExpressions, markTailFunctionCalls, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - AxisExpression
```
public AxisExpression(byte axis,
                      NodeTest nodeTest)
```
    Constructor
    
    Parameters:
    
    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
    
    See Also:
    
    Axis
- Method Detail
  - simplify
```
public Expression simplify(ExpressionVisitor visitor)
```
    Simplify an expression
    
    Overrides:
    
    simplify in class Expression
    
    Parameters:
    
    visitor - an expression visitor
    
    Returns:
    
    the simplified expression
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
```
    Type-check the expression
    
    Overrides:
    
    typeCheck in class Expression
    
    Parameters:
    
    visitor - an expression visitor
    
    contextItemType - 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
    
    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)
  - getContextItemType
```
public ItemType getContextItemType()
```
    Get the static type of the context item for this AxisExpression. May be null if not known.
    
    Returns:
    
    the statically-inferred type, or null if not known
  - 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.
    
    Overrides:
    
    optimize in class Expression
    
    Parameters:
    
    visitor - an expression visitor
    
    contextItemType - 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
    
    Returns:
    
    the original expression, rewritten if appropriate to optimize execution
  - equals
```
public boolean equals(java.lang.Object other)
```
    Is this expression the same as another expression?
    
    Overrides:
    
    equals in class java.lang.Object
  - hashCode
```
public int hashCode()
```
    get HashCode for comparing two expressions
    
    Overrides:
    
    hashCode in class java.lang.Object
  - 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
    
    Overrides:
    
    getIntrinsicDependencies in class Expression
    
    Returns:
    
    a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
  - copy
```
public Expression copy()
```
    Copy an expression. This makes a deep copy.
    
    Specified by:
    
    copy in class Expression
    
    Returns:
    
    the copy of the original 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.
    
    Overrides:
    
    computeSpecialProperties in class Expression
    
    Returns:
    
    the special properties, as a bit-significant integer
  - getItemType
```
public final ItemType getItemType(TypeHierarchy th)
```
    Determine the data type of the items returned by this expression
    
    Specified by:
    
    getItemType in class Expression
    
    Parameters:
    
    th - the type hierarchy cache
    
    Returns:
    
    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
  - computeCardinality
```
public final int computeCardinality()
```
    Specify that the expression returns a singleton
    
    Specified by:
    
    computeCardinality in class Expression
    
    Returns:
    
    the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
  - getAxis
```
public byte getAxis()
```
    Get the axis
    
    Returns:
    
    the axis number, for example Axis.CHILD
  - getNodeTest
```
public NodeTest getNodeTest()
```
    Get the NodeTest. Returns null if the AxisExpression can return any node.
    
    Returns:
    
    the node test, or null if all nodes are returned
  - 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.
    
    Overrides:
    
    addToPathMap in class Expression
    
    Parameters:
    
    pathMap - the PathMap to which the expression should be added
    
    pathMapNodeSet -
    
    Returns:
    
    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
  - iterate
```
public SequenceIterator iterate(XPathContext context)
                         throws XPathException
```
    Evaluate the path-expression in a given context to return a NodeSet
    
    Specified by:
    
    iterate in interface SequenceIterable
    
    Overrides:
    
    iterate in class Expression
    
    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
  - iterate
```
public SequenceIterator iterate(Item origin)
                         throws XPathException
```
    Iterate the axis from a given starting node, without regard to context
    
    Parameters:
    
    origin - the starting node
    
    Returns:
    
    the iterator over the axis
    
    Throws:
    
    XPathException
  - explain
```
public void explain(ExpressionPresenter destination)
```
    Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
    
    Specified by:
    
    explain in class Expression
    
    Parameters:
    
    destination - the expression presenter used to display the structure
  - toString
```
public java.lang.String toString()
```
    Represent the expression as a string for diagnostics
    
    Overrides:
    
    toString in class Expression
  - toString
```
public java.lang.String toString(NamePool pool)
```
    Represent the expression as a string for diagnostics
    
    Parameters:
    
    pool - the name pool, used for expanding names in the node test
    
    Returns:
    
    a string representation of the expression

Class AxisExpression

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.Expression

Methods inherited from class java.lang.Object

Constructor Detail

AxisExpression

Method Detail

simplify

typeCheck

getContextItemType

optimize

equals

hashCode

getIntrinsicDependencies

copy

computeSpecialProperties

getItemType

computeCardinality

getAxis

getNodeTest

addToPathMap

iterate

iterate

explain

toString

toString