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

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
`Reverser(Expression base)`

Method Summary
`int` `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`protected java.lang.String` `displayOperator(NamePool pool)` 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
`analyze, computeCardinality, display, equals, getBaseExpression, getItemType, hashCode, iterateSubExpressions, simplify`

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

`adoptChildExpression, computeDependencies, computeStaticProperties, dynamicError, dynamicError, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, 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(NamePool pool)

  Give a string representation of the operator for use in diagnostics

  Specified by:
    `displayOperator` in class `UnaryExpression`
  Returns:
    the operator, as a string