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:
Serializable, Expression

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
operands, operator
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
IdentityComparison(Expression p1, int op, Expression p2)
          Create an identity comparison identifying the two operands and the operator
 
Method Summary
 Expression analyze(StaticContext env)
          Type-check the expression
 boolean effectiveBooleanValue(XPathContext context)
          Get the effective boolean value of the expression.
 Item evaluateItem(XPathContext context)
          Evaluate the expression
 ItemType getItemType()
          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
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeCardinality, display, displayOperator, equals, getSubExpressions, hashCode, isCommutative, promote, setDetails, simplify
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSpecialProperties, iterate, markTailFunctionCalls, setLineNumber, 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. Tokenizer.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


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)

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()
Determine the data type of the expression

Returns:
Type.BOOLEAN