net.sf.saxon.expr
Class IsLastExpression

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.IsLastExpression
All Implemented Interfaces:
Expression, java.io.Serializable

public final class IsLastExpression
extends ComputedExpression

A position() eq last() expression, generated by the optimizer.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
IsLastExpression(boolean condition)
          Construct a condition that tests position() eq last() (if condition is true) or position() ne last() (if condition is false).
 
Method Summary
 Expression analyze(StaticContext env)
          Perform static analysis of an expression and its subexpressions.
 int computeCardinality()
          Determine the static cardinality
 void display(int level, NamePool pool)
          Diagnostic print of expression structure
 Item evaluateItem(XPathContext c)
          Evaluate an expression as a single item.
 boolean getCondition()
           
 int getIntrinsicDependencies()
          Get the dependencies of this expression on the context
 ItemType getItemType()
          Determine the data type of the expression
 Expression simplify()
          Simplify an expression.
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getLineNumber, getSourceLocator, getSpecialProperties, getSubExpressions, iterate, markTailFunctionCalls, promote, setLineNumber, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

IsLastExpression

public IsLastExpression(boolean condition)
Construct a condition that tests position() eq last() (if condition is true) or position() ne last() (if condition is false).

Method Detail

getCondition

public boolean getCondition()

simplify

public Expression simplify()
Description copied from class: ComputedExpression
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.

Specified by:
simplify in interface Expression
Overrides:
simplify in class ComputedExpression
Returns:
the simplified expression

analyze

public Expression analyze(StaticContext env)
Description copied from interface: Expression
Perform static analysis of an expression and its subexpressions.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables will only be accurately known if they have been explicitly declared.

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

evaluateItem

public Item evaluateItem(XPathContext c)
                  throws XPathException
Description copied from class: ComputedExpression
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.

Specified by:
evaluateItem in interface Expression
Overrides:
evaluateItem in class ComputedExpression
Parameters:
c - 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

getItemType

public ItemType getItemType()
Determine the data type of the expression

Returns:
Type.BOOLEAN

computeCardinality

public int computeCardinality()
Determine the static cardinality

Specified by:
computeCardinality in class ComputedExpression

getIntrinsicDependencies

public int getIntrinsicDependencies()
Get the dependencies of this expression on the context

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

display

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

Parameters:
level - indentation level for this expression