net.sf.saxon.expr
Class IdentityComparison

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.BinaryExpression
          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