net.sf.saxon.expr
Class ContextItemExpression

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.ContextItemExpression
All Implemented Interfaces:
Serializable, Expression

public final class ContextItemExpression
extends ComputedExpression

This class represents the expression "(dot)", which always returns the context item. This may be a AtomicValue or a Node.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
ContextItemExpression()
           
 
Method Summary
 Expression analyze(StaticContext env)
          Type-check the expression.
 int computeCardinality()
          Get the static cardinality
 void display(int level, NamePool pool)
          Diagnostic print of expression structure
 boolean equals(Object other)
          Is this expression the same as another expression?
 Item evaluateItem(XPathContext context)
          Evaluate the expression
 int getIntrinsicDependencies()
          Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
 ItemType getItemType()
          Determine the item type
 int hashCode()
          get HashCode for comparing two expressions
 SequenceIterator iterate(XPathContext context)
          Iterate over the value of the expression
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getLineNumber, getSpecialProperties, getSubExpressions, markTailFunctionCalls, promote, setLineNumber, simplify, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ContextItemExpression

public ContextItemExpression()
Method Detail

analyze

public Expression analyze(StaticContext env)
                   throws XPathException
Type-check the expression.

Parameters:
env - the static context of the expression
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)

getItemType

public ItemType getItemType()
Determine the item type

Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

computeCardinality

public int computeCardinality()
Get the static cardinality

Specified by:
computeCardinality in class ComputedExpression

equals

public boolean equals(Object other)
Is this expression the same as another expression?

Overrides:
equals in class Object

hashCode

public int hashCode()
get HashCode for comparing two expressions

Overrides:
hashCode in class Object

getIntrinsicDependencies

public int getIntrinsicDependencies()
Description copied from class: ComputedExpression
Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:
getIntrinsicDependencies in class ComputedExpression
Returns:
a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Iterate over the value of the expression

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
context - supplies the context for evaluation
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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate the expression

Specified by:
evaluateItem in interface Expression
Overrides:
evaluateItem in class ComputedExpression
Parameters:
context - The context in which the expression is to be evaluated
Returns:
the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
Throws:
XPathException - if any dynamic error occurs evaluating the expression

display

public void display(int level,
                    NamePool pool)
Diagnostic print of expression structure

Parameters:
level - indentation level for this expression