net.sf.saxon.sort

Class Reverser

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.sort.Reverser

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, Container, Expression, InstructionInfoProvider

public class Reverser
extends UnaryExpression

A Reverser is an expression that reverses the order of a sequence of items.

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.UnaryExpression

operand

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

Constructors

Constructor and Description
Reverser(Expression base)

Method Summary

Modifier and Type	Method and Description
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
protected java.lang.String	displayOperator(Configuration config) Give a string representation of the operator for use in diagnostics
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value of the expression.
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
Expression	promote(PromotionOffer offer) Promote this expression if possible

Methods inherited from class net.sf.saxon.expr.UnaryExpression

computeCardinality, display, equals, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, replaceSubExpression, simplify, typeCheck

Methods inherited from class net.sf.saxon.expr.ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Reverser

public Reverser(Expression base)

Method Detail

computeSpecialProperties

public int computeSpecialProperties()

Description copied from class: UnaryExpression

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class UnaryExpression

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException

Promote this expression if possible

Specified by:

promote in interface Expression

Overrides:

promote in class UnaryExpression

Parameters:

offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Description copied from class: ComputedExpression

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

Specified by:

iterate in interface Expression

Overrides:

iterate in class ComputedExpression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

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

displayOperator

protected java.lang.String displayOperator(Configuration config)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Parameters:

config -

Returns:

the operator, as a string