Package org.apache.commons.jxpath.ri.compiler

Class CoreOperation

java.lang.Object

org.apache.commons.jxpath.ri.compiler.Expression

org.apache.commons.jxpath.ri.compiler.Operation

org.apache.commons.jxpath.ri.compiler.CoreOperation

Direct Known Subclasses:

CoreOperationAdd, CoreOperationAnd, CoreOperationCompare, CoreOperationDivide, CoreOperationMod, CoreOperationMultiply, CoreOperationNegate, CoreOperationOr, CoreOperationRelationalExpression, CoreOperationSubtract, CoreOperationUnion

public abstract class CoreOperation
extends Operation

The common subclass for tree elements representing core operations like "+", "- ", "*" etc.

Version:

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

Author:

Dmitri Plotnikov

Nested Class Summary

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

Expression.PointerIterator, Expression.ValueIterator

Field Summary

Fields

Modifier and Type	Field	Description
protected static int	ADD_PRECEDENCE	add/subtract precedence
protected static int	AND_PRECEDENCE	and precedence
protected static int	COMPARE_PRECEDENCE	compare precedence
protected static int	MULTIPLY_PRECEDENCE	multiply/divide/mod precedence
protected static int	NEGATE_PRECEDENCE	negate precedence
protected static int	OR_PRECEDENCE	or precedence
protected static int	RELATIONAL_EXPR_PRECEDENCE	relational expression precedence
protected static int	UNION_PRECEDENCE	union precedence

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

NOT_A_NUMBER, ONE, ZERO

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

args

Constructor Summary

Constructors

Constructor	Description
CoreOperation(Expression[] args)	Create a new CoreOperation.

Method Summary

Modifier and Type	Method	Description
java.lang.Object	compute(EvalContext context)	Evaluates the expression.
abstract java.lang.Object	computeValue(EvalContext context)	Evaluates the expression.
protected abstract int	getPrecedence()	Computes the precedence of the operation.
abstract java.lang.String	getSymbol()	Returns the XPath symbol for this operation, e.g.
protected abstract boolean	isSymmetric()	Returns true if the operation is not sensitive to the order of arguments, e.g.
private java.lang.String	parenthesize(Expression expression, boolean left)	Wrap an expression in parens if necessary.
java.lang.String	toString()

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

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

computeContextDependent, getArguments

Field Detail

OR_PRECEDENCE

protected static final int OR_PRECEDENCE

or precedence

See Also:

Constant Field Values

AND_PRECEDENCE

protected static final int AND_PRECEDENCE

and precedence

See Also:

Constant Field Values

COMPARE_PRECEDENCE

protected static final int COMPARE_PRECEDENCE

compare precedence

See Also:

Constant Field Values

RELATIONAL_EXPR_PRECEDENCE

protected static final int RELATIONAL_EXPR_PRECEDENCE

relational expression precedence

See Also:

Constant Field Values

ADD_PRECEDENCE

protected static final int ADD_PRECEDENCE

add/subtract precedence

See Also:

Constant Field Values

MULTIPLY_PRECEDENCE

protected static final int MULTIPLY_PRECEDENCE

multiply/divide/mod precedence

See Also:

Constant Field Values

NEGATE_PRECEDENCE

protected static final int NEGATE_PRECEDENCE

negate precedence

See Also:

Constant Field Values

UNION_PRECEDENCE

protected static final int UNION_PRECEDENCE

union precedence

See Also:

Constant Field Values

Constructor Detail

CoreOperation

public CoreOperation(Expression[] args)

Create a new CoreOperation.

Parameters:

args - Expression[]

Method Detail

compute

public java.lang.Object compute(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:

compute in class Expression

Parameters:

context - evaluation context

Returns:

Object

computeValue

public abstract 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 Expression

Parameters:

context - evaluation context

Returns:

Object

getSymbol

public abstract java.lang.String getSymbol()

Returns the XPath symbol for this operation, e.g. "+", "div", etc.

Returns:

String symbol

isSymmetric

protected abstract boolean isSymmetric()

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".

Returns:

boolean

getPrecedence

protected abstract int getPrecedence()

Computes the precedence of the operation.

Returns:

int precedence

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

parenthesize

private java.lang.String parenthesize(Expression expression,
                                      boolean left)

Wrap an expression in parens if necessary.

Parameters:

expression - other Expression

left - whether expression is left of this one.

Returns:

String