net.sf.saxon.expr
Class VennExpression

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

public class VennExpression
extends BinaryExpression

An expression representing a nodeset that is a union, difference, or intersection of two other NodeSets

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.BinaryExpression
operands, operator
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
VennExpression(Expression p1, int op, Expression p2)
          Constructor
 
Method Summary
 Expression analyze(StaticContext env)
          Type-check the expression
 int computeCardinality()
          Determine the static cardinality of the expression
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 boolean effectiveBooleanValue(XPathContext context)
          Get the effective boolean value.
 ItemType getItemType()
          Determine the data type of the items returned by this expression
 int hashCode()
          Is this expression the same as another expression?
 SequenceIterator iterate(XPathContext c)
          Iterate over the value of the expression.
 Expression simplify()
          Simplify the expression
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
display, displayOperator, equals, getSubExpressions, isCommutative, promote, setDetails
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeStaticProperties, dynamicError, evaluateAsString, evaluateItem, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSpecialProperties, markTailFunctionCalls, setLineNumber, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

VennExpression

public VennExpression(Expression p1,
                      int op,
                      Expression p2)
Constructor

Parameters:
p1 - the left-hand operand
op - the operator (union, intersection, or difference)
p2 - the right-hand operand
Method Detail

getItemType

public final ItemType getItemType()
Determine the data type of the items returned by this expression

Returns:
the data type

computeCardinality

public final int computeCardinality()
Determine the static cardinality of the expression

Overrides:
computeCardinality in class BinaryExpression

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 ComputedExpression

simplify

public Expression simplify()
                    throws XPathException
Simplify the expression

Specified by:
simplify in interface Expression
Overrides:
simplify in class BinaryExpression
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

analyze

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

Specified by:
analyze in interface Expression
Overrides:
analyze in class BinaryExpression
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)

hashCode

public int hashCode()
Is this expression the same as another expression?

Overrides:
hashCode in class BinaryExpression

iterate

public SequenceIterator iterate(XPathContext c)
                         throws XPathException
Iterate over the value of the expression. The result will always be sorted in document order, with duplicates eliminated

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
c - The context for evaluation
Returns:
a SequenceIterator representing the union of the two operands
Throws:
XPathException - if any dynamic error occurs evaluating the expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
Get the effective boolean value. In the case of a union expression, this is reduced to an OR expression, for efficiency

Specified by:
effectiveBooleanValue in interface Expression
Overrides:
effectiveBooleanValue in class ComputedExpression
Parameters:
context - The context in which the expression is to be evaluated
Returns:
the effective boolean value
Throws:
XPathException - if any dynamic error occurs evaluating the expression