Choose

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.instruct.Instruction
  - - net.sf.saxon.expr.instruct.Choose

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, TailCallReturner, InstructionInfo, Locator
```
public class Choose
extends Instruction
```
Compiled representation of an xsl:choose or xsl:if element in the stylesheet. Also used for typeswitch in XQuery.

See Also:
Serialized Form

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD

Constructor Summary

Constructors
Constructor and Description

Choose(Expression[] conditions, Expression[] actions)
Construct an xsl:choose instruction

Constructors
Constructor and Description
`Choose(Expression[] conditions, Expression[] actions)` Construct an xsl:choose instruction

Method Summary

Methods
Modifier and Type	Method and Description
`PathMap.PathMapNodeSet`	`addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)` Add a representation of this expression to a PathMap.
`void`	`checkForUpdatingSubexpressions()` Check to ensure that this expression does not contain any updating subexpressions.
`void`	`checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole)` Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
`int`	`computeCardinality()` Compute the cardinality of the sequence returned by evaluating this instruction
`int`	`computeSpecialProperties()` Get the static properties of this expression (other than its type).
`Expression`	`copy()` Copy an expression.
`boolean`	`createsNewNodes()` Determine whether this instruction creates new nodes.
`Item`	`evaluateItem(XPathContext context)` Evaluate an expression as a single item.
`void`	`evaluatePendingUpdates(XPathContext context, PendingUpdateList pul)` Evaluate an updating expression, adding the results to a Pending Update List.
`void`	`explain(ExpressionPresenter out)` Diagnostic print of expression structure.
`Expression[]`	`getActions()` Get the array of actions to be performed
`Expression[]`	`getConditions()` Get the array of conditions to be tested
`ExpressionCompiler`	`getExpressionCompiler()` Return the compiler of the Choose expression
`int`	`getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`int`	`getInstructionNameCode()` Get the name of this instruction for diagnostic and tracing purposes We assume that if there was only one condition then it was an xsl:if; this is not necessarily so, but it's adequate for tracing purposes.
`ItemType`	`getItemType(TypeHierarchy th)` Get the item type of the items returned by evaluating this instruction
`int`	`getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons)` Get the "sweep" of this expression as defined in the W3C streamability specifications.
`ChooseAdjunct`	`getStreamingAdjunct()` Get a class that supports streamed evaluation of this expression
`boolean`	`implementsStaticTypeCheck()` Determine whether this expression implements its own method for static type checking
`static boolean`	`isSingleBranchChoice(Expression exp)` Test whether an expression is a single-branch choose, that is, an expression of the form if (condition) then exp else ()
`boolean`	`isUpdatingExpression()` Determine whether this is an updating expression as defined in the XQuery update specification
`boolean`	`isVacuousExpression()` Determine whether this is a vacuous expression as defined in the XQuery update specification
`SequenceIterator<? extends Item>`	`iterate(XPathContext context)` Return an Iterator to iterate over the values of a sequence.
`EventIterator`	`iterateEvents(XPathContext context)` Deliver the result of the expression as a sequence of events.
`Iterator<SubExpressionInfo>`	`iterateSubExpressionInfo()` Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
`Iterator<Expression>`	`iterateSubExpressions()` Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
`static Expression`	`makeConditional(Expression condition, Expression thenExp)` Make a simple conditional expression (if (condition) then (thenExp) else ()
`static Expression`	`makeConditional(Expression condition, Expression thenExp, Expression elseExp)` Make a simple conditional expression (if (condition) then (thenExp) else (elseExp)
`int`	`markTailFunctionCalls(StructuredQName qName, int arity)` Mark tail-recursive calls on functions.
`Expression`	`optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`TailCall`	`processLeavingTail(XPathContext context)` Process this instruction, that is, choose an xsl:when or xsl:otherwise child and process it.
`protected void`	`promoteInst(PromotionOffer offer)` Handle promotion offers, that is, non-local tree rewrites.
`boolean`	`replaceSubExpression(Expression original, Expression replacement)` Replace one subexpression by a replacement subexpression
`Expression`	`simplify(ExpressionVisitor visitor)` Simplify an expression.
`Expression`	`staticTypeCheck(SequenceType req, boolean backwardsCompatible, RoleLocator role, TypeCheckerEnvironment visitor)` Static type checking for conditional expressions is delegated to the expression itself, and is performed separately on each branch of the conditional, so that dynamic checks are added only on those branches where the check is actually required.
`Pattern`	`toStreamingPattern(Configuration config, List<String> reasonForFailure)` Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
`String`	`toString()` The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
`Expression`	`typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.instruct.Instruction
assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getExpressionName, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promote

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

Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId

- Constructor Detail
  - Choose
```
public Choose(Expression[] conditions,
      Expression[] actions)
```
    Construct an xsl:choose instruction
    
    Parameters:
    conditions - the conditions to be tested, in order
    actions - the actions to be taken when the corresponding condition is true
- Method Detail
  - makeConditional
```
public static Expression makeConditional(Expression condition,
                         Expression thenExp,
                         Expression elseExp)
```
    Make a simple conditional expression (if (condition) then (thenExp) else (elseExp)
    
    Parameters:
    condition - the condition to be tested
    thenExp - the expression to be evaluated if the condition is true
    elseExp - the expression to be evaluated if the condition is false
    
    Returns:
    the expression
  - makeConditional
```
public static Expression makeConditional(Expression condition,
                         Expression thenExp)
```
    Make a simple conditional expression (if (condition) then (thenExp) else ()
    
    Parameters:
    condition - the condition to be tested
    thenExp - the expression to be evaluated if the condition is true
    
    Returns:
    the expression
  - isSingleBranchChoice
```
public static boolean isSingleBranchChoice(Expression exp)
```
    Test whether an expression is a single-branch choose, that is, an expression of the form if (condition) then exp else ()
    
    Parameters:
    exp - the expression to be tested
    
    Returns:
    true if the expression is a choose expression and there is only one condition, so that the expression returns () if this condition is false
  - getConditions
```
public Expression[] getConditions()
```
    Get the array of conditions to be tested
    
    Returns:
    the array of condition expressions
  - getActions
```
public Expression[] getActions()
```
    Get the array of actions to be performed
    
    Returns:
    the array of expressions to be evaluated when the corresponding condition is true
  - getInstructionNameCode
```
public int getInstructionNameCode()
```
    Get the name of this instruction for diagnostic and tracing purposes We assume that if there was only one condition then it was an xsl:if; this is not necessarily so, but it's adequate for tracing purposes.
    
    Overrides:
    
    getInstructionNameCode in class Instruction
    
    Returns:
    a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
  - simplify
```
public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
```
    Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).
    
    Specified by:
    
    simplify in class Instruction
    
    Parameters:
    visitor - expression visitor object
    
    Returns:
    the simplified expression
    
    Throws:
    
    XPathException - if an error is discovered during expression rewriting
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                   ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException
```
    Description copied from class: Expression
    
    Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.
    
    This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
    
    This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
    
    If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
    
    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)
  - implementsStaticTypeCheck
```
public boolean implementsStaticTypeCheck()
```
    Determine whether this expression implements its own method for static type checking
    
    Overrides:
    
    implementsStaticTypeCheck in class Expression
    
    Returns:
    true - this expression has a non-trivial implementation of the staticTypeCheck() method
  - staticTypeCheck
```
public Expression staticTypeCheck(SequenceType req,
                         boolean backwardsCompatible,
                         RoleLocator role,
                         TypeCheckerEnvironment visitor)
                           throws XPathException
```
    Static type checking for conditional expressions is delegated to the expression itself, and is performed separately on each branch of the conditional, so that dynamic checks are added only on those branches where the check is actually required. This also results in a static type error if any branch is incapable of delivering a value of the required type. One reason for this approach is to avoid doing dynamic type checking on a recursive function call as this prevents tail-call optimization being used.
    
    Overrides:
    
    staticTypeCheck in class Expression
    
    Parameters:
    req - the required type
    backwardsCompatible - true if backwards compatibility mode applies
    role - the role of the expression in relation to the required type
    visitor - an expression visitor
    
    Returns:
    the expression after type checking (perhaps augmented with dynamic type checking code)
    
    Throws:
    
    XPathException - if failures occur, for example if the static type of one branch of the conditional is incompatible with the required type
  - 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)
  - 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
  - checkForUpdatingSubexpressions
```
public void checkForUpdatingSubexpressions()
                                    throws XPathException
```
    Check to ensure that this expression does not contain any updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.
    
    Overrides:
    
    checkForUpdatingSubexpressions in class Expression
    
    Throws:
    
    XPathException - if the expression has a non-permitted updateing subexpression
  - isUpdatingExpression
```
public boolean isUpdatingExpression()
```
    Determine whether this is an updating expression as defined in the XQuery update specification
    
    Overrides:
    
    isUpdatingExpression in class Expression
    
    Returns:
    true if this is an updating expression
  - isVacuousExpression
```
public boolean isVacuousExpression()
```
    Determine whether this is a vacuous expression as defined in the XQuery update specification
    
    Overrides:
    
    isVacuousExpression in class Expression
    
    Returns:
    true if this expression is vacuous
  - 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 prefered. For instructions this is the process() method.
    
    Overrides:
    
    getImplementationMethod in class Instruction
    
    Returns:
    the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD
  - markTailFunctionCalls
```
public int markTailFunctionCalls(StructuredQName qName,
                        int arity)
```
    Mark tail-recursive calls on functions. For most expressions, this does nothing.
    
    Overrides:
    
    markTailFunctionCalls in class Expression
    
    Parameters:
    qName - the name of the function
    arity - the arity (number of parameters) of the function
    
    Returns:
    0 if no tail call was found; 1 if a tail call on a different function was found; 2 if a tail recursive call was found and if this call accounts for the whole of the value.
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Get the item type of the items returned by evaluating this instruction
    
    Overrides:
    
    getItemType in class Instruction
    
    Parameters:
    th - Type hierarchy cache
    
    Returns:
    the static item type of the instruction
  - computeCardinality
```
public int computeCardinality()
```
    Compute the cardinality of the sequence returned by evaluating this instruction
    
    Overrides:
    
    computeCardinality in class Instruction
    
    Returns:
    the static cardinality
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    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 Instruction
    
    Returns:
    a set of flags indicating static properties of this expression
  - createsNewNodes
```
public final boolean createsNewNodes()
```
    Determine whether this instruction creates new nodes. This implementation returns true if any of the "actions" creates new nodes. (Nodes created by the conditions can't contribute to the result).
    
    Overrides:
    
    createsNewNodes in class Instruction
    
    Returns:
    true if the instruction creates new nodes (or if it can't be proved that it doesn't)
  - getStreamability
```
public int getStreamability(int syntacticContext,
                   boolean allowExtensions,
                   List<String> reasons)
```
    Description copied from class: Expression
    
    Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon
    
    Overrides:
    
    getStreamability in class Expression
    
    Parameters:
    syntacticContext - one of the values Expression.NAVIGATION_CONTEXT, Expression.NODE_VALUE_CONTEXT, Expression.INHERITED_CONTEXT, Expression.INSPECTION_CONTEXT
    allowExtensions - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some
    reasons - the caller may supply a list, in which case the implementation may add to this list a message explaining why the construct is not streamable, suitable for inclusion in an error message.
    
    Returns:
    one of the values Expression.W3C_MOTIONLESS, Expression.W3C_CONSUMING, Expression.W3C_GROUP_CONSUMING, Expression.W3C_FREE_RANGING
  - getStreamingAdjunct
```
public ChooseAdjunct getStreamingAdjunct()
```
    Get a class that supports streamed evaluation of this expression
    
    Overrides:
    
    getStreamingAdjunct in class Expression
    
    Returns:
    the relevant StreamingAdjunct, or null if none is available
  - toStreamingPattern
```
public Pattern toStreamingPattern(Configuration config,
                         List<String> reasonForFailure)
```
    Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
    
    Overrides:
    
    toStreamingPattern in class Expression
    
    Parameters:
    config - the Saxon configuration
    reasonForFailure - a list which will be populated with messages giving reasons why the expression cannot be converted
    
    Returns:
    the equivalent pattern if conversion succeeds; otherwise null
  - iterateSubExpressions
```
public Iterator<Expression> iterateSubExpressions()
```
    Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
    
    Overrides:
    
    iterateSubExpressions in class Expression
    
    Returns:
    an iterator containing the sub-expressions of this expression
  - iterateSubExpressionInfo
```
public Iterator<SubExpressionInfo> iterateSubExpressionInfo()
```
    Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
    
    Overrides:
    
    iterateSubExpressionInfo 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
  - promoteInst
```
protected void promoteInst(PromotionOffer offer)
                    throws XPathException
```
    Handle promotion offers, that is, non-local tree rewrites.
    
    Overrides:
    
    promoteInst in class Instruction
    
    Parameters:
    offer - The type of rewrite being offered
    
    Throws:
    
    XPathException
  - checkPermittedContents
```
public void checkPermittedContents(SchemaType parentType,
                          StaticContext env,
                          boolean whole)
                            throws XPathException
```
    Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
    
    Overrides:
    
    checkPermittedContents in class Expression
    
    Parameters:
    parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
    env - the static context
    whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
    
    Throws:
    
    XPathException - if the value delivered by this expression cannot be part of the content model of the given type
  - addToPathMap
```
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                  PathMap.PathMapNodeSet pathMapNodeSet)
```
    Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.
    
    The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.
    
    Overrides:
    
    addToPathMap in class Expression
    
    Parameters:
    pathMap - the PathMap to which the expression should be added
    pathMapNodeSet - the set of PathMap nodes to which the paths from this expression should be appended
    
    Returns:
    the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.
  - toString
```
public String toString()
```
    The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
    
    Overrides:
    
    toString in class Expression
    
    Returns:
    a representation of the expression as a string
  - 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
  - processLeavingTail
```
public TailCall processLeavingTail(XPathContext context)
                            throws XPathException
```
    Process this instruction, that is, choose an xsl:when or xsl:otherwise child and process it.
    
    Specified by:
    
    processLeavingTail in interface TailCallReturner
    
    Specified by:
    
    processLeavingTail in class Instruction
    
    Parameters:
    context - the dynamic context of this transformation
    
    Returns:
    a TailCall, if the chosen branch ends with a call of call-template or apply-templates. It is the caller's responsibility to execute such a TailCall. If there is no TailCall, returns null.
    
    Throws:
    
    XPathException - if any non-recoverable dynamic error occurs
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
    
    Overrides:
    
    evaluateItem in class Instruction
    
    Parameters:
    context - The context in which the expression is to be evaluated
    
    Returns:
    the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - iterate
```
public SequenceIterator<? extends Item> 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 relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence. In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.
    
    Overrides:
    
    iterate in class Instruction
    
    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
  - iterateEvents
```
public EventIterator iterateEvents(XPathContext context)
                            throws XPathException
```
    Deliver the result of the expression as a sequence of events.
    
    The events (of class PullEvent) are either complete items, or one of startElement, endElement, startDocument, or endDocument, known as semi-nodes. The stream of events may also include a nested EventIterator. If a start-end pair exists in the sequence, then the events between this pair represent the content of the document or element. The content sequence will have been processed to the extent that any attribute and namespace nodes in the content sequence will have been merged into the startElement event. Namespace fixup will have been performed: that is, unique prefixes will have been allocated to element and attribute nodes, and all namespaces will be declared by means of a namespace node in the startElement event or in an outer startElement forming part of the sequence. However, duplicate namespaces may appear in the sequence.
    
    The content of an element or document may include adjacent or zero-length text nodes, atomic values, and nodes represented as nodes rather than broken down into events.
    
    Overrides:
    
    iterateEvents in class Expression
    
    Parameters:
    context - The dynamic evaluation context
    
    Returns:
    the result of the expression as an iterator over a sequence of PullEvent objects
    
    Throws:
    
    XPathException - if a dynamic error occurs during expression evaluation
  - evaluatePendingUpdates
```
public void evaluatePendingUpdates(XPathContext context,
                          PendingUpdateList pul)
                            throws XPathException
```
    Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException
    
    Overrides:
    
    evaluatePendingUpdates in class Expression
    
    Parameters:
    context - the XPath dynamic evaluation context
    pul - the pending update list to which the results should be written
    
    Throws:
    
    XPathException - if evaluation fails
  - getExpressionCompiler
```
public ExpressionCompiler getExpressionCompiler()
```
    Return the compiler of the Choose expression
    
    Overrides:
    
    getExpressionCompiler in class Expression
    
    Returns:
    the relevant ExpressionCompiler

Class Choose

Field Summary

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

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.instruct.Instruction

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

Methods inherited from class java.lang.Object

Methods inherited from interface javax.xml.transform.SourceLocator

Constructor Detail

Choose

Method Detail

makeConditional

makeConditional

isSingleBranchChoice

getConditions

getActions

getInstructionNameCode

simplify

typeCheck

implementsStaticTypeCheck

staticTypeCheck

optimize

copy

checkForUpdatingSubexpressions

isUpdatingExpression

isVacuousExpression

getImplementationMethod

markTailFunctionCalls

getItemType

computeCardinality

computeSpecialProperties

createsNewNodes

getStreamability

getStreamingAdjunct

toStreamingPattern

iterateSubExpressions

iterateSubExpressionInfo

replaceSubExpression

promoteInst

checkPermittedContents

addToPathMap

toString

explain

processLeavingTail

evaluateItem

iterate

iterateEvents

evaluatePendingUpdates

getExpressionCompiler