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## net.sf.saxon.expr.sort
Class ConditionalSorter

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.sort.ConditionalSorter

All Implemented Interfaces:
  Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

    public class ConditionalSorter

extends Expression

An expression that sorts an underlying sequence into document order if some condition is true, or that returns the sequence "as is" (knowing that it doesn't need sorting) if the condition is false.

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression
`EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD`

Constructor Summary
`ConditionalSorter(Expression condition, DocumentSorter sorter)` Create a conditional document sorter

Method Summary
`protected int` | `computeCardinality()` Compute the static cardinality of this expression
`protected int` | `computeSpecialProperties()` Compute the special properties of this expression.
`Expression` | `copy()` Copy an expression.
`void` | `explain(ExpressionPresenter out)` Diagnostic print of expression structure.
`int` | `getCardinality()` Determine the static cardinality of the expression.
`Expression` | `getCondition()` Get the condition under which the nodes need to be sorted
`DocumentSorter` | `getDocumentSorter()` Get the document sorter, which sorts the nodes if the condition is true
`int` | `getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`ItemType` | `getItemType(TypeHierarchy th)` Determine the data type of the expression, if possible.
`SequenceIterator` | `iterate(XPathContext context)` Return an Iterator to iterate over the values of a sequence.
`Iterator<Expression>` | `iterateSubExpressions()` Get the immediate sub-expressions of this expression.
`Expression` | `optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`Expression` | `promote(PromotionOffer offer, Expression parent)` Offer promotion for this subexpression.
`boolean` | `replaceSubExpression(Expression original, Expression replacement)` Replace one subexpression by a replacement subexpression
`Expression` | `typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.Expression
`addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeError`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### ConditionalSorter

    public ConditionalSorter(Expression condition,
                             DocumentSorter sorter)

  Create a conditional document sorter

  Parameters:
    `condition` - the conditional expression
    `sorter` - the sorting expression

Method Detail

### getCondition

    public Expression getCondition()

  Get the condition under which the nodes need to be sorted

  Returns:
    the condition (an expression)

### getDocumentSorter

    public DocumentSorter getDocumentSorter()

  Get the document sorter, which sorts the nodes if the condition is true

  Returns:
    the document sorter

### typeCheck

    public Expression typeCheck(ExpressionVisitor visitor,
                                ExpressionVisitor.ContextItemType contextItemType)
                         throws XPathException

  Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

  Overrides:
    `typeCheck` in class `Expression`
  Parameters:
    `visitor` - an expression visitor
    `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
  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)

### getCardinality

    public int getCardinality()

  Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

  Overrides:
    `getCardinality` in class `Expression`
  Returns:
    one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

### computeSpecialProperties

    protected int computeSpecialProperties()

  Compute the special properties of this expression. These properties are denoted by a bit-significant integer, possible values are in class `StaticProperty`. The "special" properties are properties other than cardinality and dependencies, and most of them relate to properties of node sequences, for example whether the nodes are in document order.

  Overrides:
    `computeSpecialProperties` in class `Expression`
  Returns:
    the special properties, as a bit-significant integer

### getImplementationMethod

    public int getImplementationMethod()

  An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

  Overrides:
    `getImplementationMethod` in class `Expression`
  Returns:
    the implementation method, for example `Expression.ITERATE_METHOD` or `Expression.EVALUATE_METHOD` or `Expression.PROCESS_METHOD`

### iterateSubExpressions

    public Iterator<Expression> iterateSubExpressions()

  Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

  Overrides:
    `iterateSubExpressions` in class `Expression`
  Returns:
    an iterator containing the sub-expressions of this expression

### replaceSubExpression

    public boolean replaceSubExpression(Expression original,
                                        Expression replacement)

  Replace one subexpression by a replacement subexpression

  Overrides:
    `replaceSubExpression` in class `Expression`
  Parameters:
    `original` - the original subexpression
    `replacement` - the replacement subexpression
  Returns:
    true if the original subexpression is found

### optimize

    public Expression optimize(ExpressionVisitor visitor,
                               ExpressionVisitor.ContextItemType contextItemType)
                        throws XPathException

  Description copied from class: `Expression`
  Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

  This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

  Overrides:
    `optimize` in class `Expression`
  Parameters:
    `visitor` - an expression visitor
    `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
  Returns:
    the original expression, rewritten if appropriate to optimize execution
  Throws:
    `XPathException` - if an error is discovered during this phase (typically a type error)

### computeCardinality

    protected int computeCardinality()

  Compute the static cardinality of this expression

  Specified by:
    `computeCardinality` in class `Expression`
  Returns:
    the computed cardinality, as one of the values `StaticProperty.ALLOWS_ZERO_OR_ONE`, `StaticProperty.EXACTLY_ONE`, `StaticProperty.ALLOWS_ONE_OR_MORE`, `StaticProperty.ALLOWS_ZERO_OR_MORE`

### copy

    public Expression copy()

  Copy an expression. This makes a deep copy.

  Specified by:
    `copy` in class `Expression`
  Returns:
    the copy of the original expression

### explain

    public void explain(ExpressionPresenter out)

  Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

  Specified by:
    `explain` in class `Expression`
  Parameters:
    `out` - the expression presenter used to display the structure

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

  This method should always return a result, though it may be the best approximation that is available at the time.

  Specified by:
    `getItemType` in class `Expression`
  Parameters:
    `th` - the type hierarchy cache
  Returns:
    a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

### promote

    public Expression promote(PromotionOffer offer,
                              Expression parent)
                       throws XPathException

  Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

  Overrides:
    `promote` in class `Expression`
  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
    `parent` -
  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

  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.

  Overrides:
    `iterate` in class `Expression`
  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

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