org.apache.commons.jxpath.ri.compiler
Class CoreOperationRelationalExpression

java.lang.Object
  org.apache.commons.jxpath.ri.compiler.Expression
      org.apache.commons.jxpath.ri.compiler.Operation
          org.apache.commons.jxpath.ri.compiler.CoreOperation
              org.apache.commons.jxpath.ri.compiler.CoreOperationRelationalExpression

Direct Known Subclasses:

CoreOperationGreaterThan, CoreOperationGreaterThanOrEqual, CoreOperationLessThan, CoreOperationLessThanOrEqual

public abstract class CoreOperationRelationalExpression
extends CoreOperation

Base implementation of Expression for the operations ">", ">=", "<", "<=".

Since:

JXPath 1.3

Version:

$Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $

Author:

Matt Benson

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.commons.jxpath.ri.compiler.Expression

Expression.PointerIterator, Expression.ValueIterator

Field Summary

Fields inherited from class org.apache.commons.jxpath.ri.compiler.CoreOperation

ADD_PRECEDENCE, AND_PRECEDENCE, COMPARE_PRECEDENCE, MULTIPLY_PRECEDENCE, NEGATE_PRECEDENCE, OR_PRECEDENCE, RELATIONAL_EXPR_PRECEDENCE, UNION_PRECEDENCE

Fields inherited from class org.apache.commons.jxpath.ri.compiler.Operation

args

Fields inherited from class org.apache.commons.jxpath.ri.compiler.Expression

NOT_A_NUMBER, ONE, ZERO

Constructor Summary

protected

CoreOperationRelationalExpression(Expression[] args) Create a new CoreOperationRelationalExpression.

Method Summary

private boolean	compute(java.lang.Object left, java.lang.Object right) Compare left to right.
java.lang.Object	computeValue(EvalContext context) Evaluates the expression.
private boolean	containsMatch(java.util.Iterator it, java.lang.Object value) Learn whether any element returned from an Iterator matches a given value.
protected abstract boolean	evaluateCompare(int compare) Template method for subclasses to evaluate the result of a comparison.
private boolean	findMatch(java.util.Iterator lit, java.util.Iterator rit) Learn whether there is an intersection between two Iterators.
protected int	getPrecedence() Computes the precedence of the operation.
protected boolean	isSymmetric() Returns true if the operation is not sensitive to the order of arguments, e.g.
private java.lang.Object	reduce(java.lang.Object o) Reduce an operand for comparison.

Methods inherited from class org.apache.commons.jxpath.ri.compiler.CoreOperation

compute, getSymbol, toString

Methods inherited from class org.apache.commons.jxpath.ri.compiler.Operation

computeContextDependent, getArguments

Methods inherited from class org.apache.commons.jxpath.ri.compiler.Expression

isContextDependent, iterate, iteratePointers

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

CoreOperationRelationalExpression

protected CoreOperationRelationalExpression(Expression[] args)

Create a new CoreOperationRelationalExpression.

Parameters:

args - arguments

Method Detail

computeValue

public final java.lang.Object computeValue(EvalContext context)

Description copied from class: Expression

Evaluates the expression. If the result is a node set, returns the first element of the node set.

Specified by:

computeValue in class CoreOperation

Parameters:

context - evaluation context

Returns:

Object

getPrecedence

protected final int getPrecedence()

Description copied from class: CoreOperation

Computes the precedence of the operation.

Specified by:

getPrecedence in class CoreOperation

Returns:

int precedence

isSymmetric

protected final boolean isSymmetric()

Description copied from class: CoreOperation

Returns true if the operation is not sensitive to the order of arguments, e.g. "=", "and" etc, and false if it is, e.g. "<=", "div".

Specified by:

isSymmetric in class CoreOperation

Returns:

boolean

evaluateCompare

protected abstract boolean evaluateCompare(int compare)

Template method for subclasses to evaluate the result of a comparison.

Parameters:

compare - result of comparison to evaluate

Returns:

ultimate operation success/failure

compute

private boolean compute(java.lang.Object left,
                        java.lang.Object right)

Compare left to right.

Parameters:

left - left operand

right - right operand

Returns:

operation success/failure

reduce

private java.lang.Object reduce(java.lang.Object o)

Reduce an operand for comparison.

Parameters:

o - Object to reduce

Returns:

reduced operand

containsMatch

private boolean containsMatch(java.util.Iterator it,
                              java.lang.Object value)

Learn whether any element returned from an Iterator matches a given value.

Parameters:

it - Iterator

value - to look for

Returns:

whether a match was found

findMatch

private boolean findMatch(java.util.Iterator lit,
                          java.util.Iterator rit)

Learn whether there is an intersection between two Iterators.

Parameters:

lit - left Iterator

rit - right Iterator

Returns:

whether a match was found