net.sf.saxon.expr
Class IdentityComparison

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

public final class IdentityComparison
extends BinaryExpression

IdentityComparison: a boolean expression that compares two nodes for equals, not-equals, greater-than or less-than based on identity and document ordering

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
IdentityComparison(Expression p1, int op, Expression p2)
          Create an identity comparison identifying the two operands and the operator
 
Method Summary
 boolean effectiveBooleanValue(XPathContext context)
          Get the effective boolean value of the expression.
 Item evaluateItem(XPathContext context)
          Evaluate the expression
 ItemType getItemType(TypeHierarchy th)
          Determine the data type of the expression
 void setGenerateIdEmulation(boolean flag)
          Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's
 Expression typeCheck(StaticContext env, ItemType contextItemType)
          Type-check the expression
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeCardinality, computeSpecialProperties, display, displayOperator, equals, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, optimize, promote, simplify
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

IdentityComparison

public IdentityComparison(Expression p1,
                          int op,
                          Expression p2)
Create an identity comparison 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

setGenerateIdEmulation

public void setGenerateIdEmulation(boolean flag)
Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's


typeCheck

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

Specified by:
typeCheck in interface Expression
Overrides:
typeCheck in class BinaryExpression
Parameters:
env - the static context of the expression
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:
StaticError - if an error is discovered during this phase (typically a type error)
XPathException

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

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
Description copied from class: ComputedExpression
Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.

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

getItemType

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

Parameters:
th -
Returns:
Type.BOOLEAN