net.sf.saxon.expr
Class ValueComparison

java.lang.Object
  extended bynet.sf.saxon.expr.ComputedExpression
      extended bynet.sf.saxon.expr.BinaryExpression
          extended bynet.sf.saxon.expr.ValueComparison
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public final class ValueComparison
extends BinaryExpression

ValueComparison: a boolean expression that compares two atomic values for equals, not-equals, greater-than or less-than. Implements the operators eq, ne, lt, le, gt, ge

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.BinaryExpression
operand0, operand1, operator
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
ValueComparison(Expression p1, int op, Expression p2)
          Create a relational expression identifying the two operands and the operator
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Type-check the expression
 boolean effectiveBooleanValue(XPathContext context)
          Evaluate the expression in a boolean context
 Item evaluateItem(XPathContext context)
          Evaluate the expression in a given context
 ItemType getItemType()
          Determine the data type of the expression
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeCardinality, computeSpecialProperties, display, displayOperator, equals, getOperands, getOperator, hashCode, isCommutative, isInverse, iterateSubExpressions, promote, simplify
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ValueComparison

public ValueComparison(Expression p1,
                       int op,
                       Expression p2)
Create a relational expression identifying the two operands and the operator

Parameters:
p1 - the left-hand operand
op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
p2 - the right-hand operand
Method Detail

analyze

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

Specified by:
analyze in interface Expression
Overrides:
analyze in class BinaryExpression
Throws:
XPathException

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
Evaluate the expression in a boolean context

Specified by:
effectiveBooleanValue in interface Expression
Overrides:
effectiveBooleanValue in class ComputedExpression
Parameters:
context - the given context for evaluation
Returns:
a boolean representing the result of the numeric comparison of the two operands
Throws:
XPathException - if any dynamic error occurs evaluating the expression

evaluateItem

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

Specified by:
evaluateItem in interface Expression
Overrides:
evaluateItem in class ComputedExpression
Parameters:
context - the given context for evaluation
Returns:
a BooleanValue representing the result of the numeric comparison of the two operands, or null representing the 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