net.sf.saxon.expr.instruct

Class WherePopulated

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.instruct.WherePopulated

All Implemented Interfaces:

ExportAgent, ItemMappingFunction<Item<?>,Item<?>>, Locatable, IdentityComparable

public class WherePopulated
extends UnaryExpression
implements ItemMappingFunction<Item<?>,Item<?>>

A compiled xsl:where-populated instruction (formerly xsl:conditional-content).

Field Summary

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
WherePopulated(Expression base) Create the instruction

Method Summary

Modifier and Type	Method and Description
int	computeCardinality() Determine the static cardinality.
Expression	copy(RebindingMap rebindings) Copy an expression.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
protected OperandRole	getOperandRole() Get the usage (in terms of streamability analysis) of the single operand
String	getStreamerName() Get the (partial) name of a class that supports streaming of this kind of expression
static boolean	isDeemedEmpty(Item item) Test whether an item is empty according to the definition in the spec for xsl:conditional-content
boolean	isInstruction() Ask whether this expression is an instruction.
SequenceIterator<?>	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
Item	mapItem(Item item) Map one item to another item.

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

computeHashCode, computeSpecialProperties, displayOperator, equals, getBaseExpression, getItemType, getOperand, operands, optimize, setBaseExpression, toShortString, toString, typeCheck

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

WherePopulated

public WherePopulated(Expression base)

Create the instruction

Method Detail

isInstruction

public boolean isInstruction()

Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs.

Overrides:

isInstruction in class Expression

Returns:

true if this construct originates as an XSLT instruction

getOperandRole

protected OperandRole getOperandRole()

Get the usage (in terms of streamability analysis) of the single operand

Specified by:

getOperandRole in class UnaryExpression

Returns:

the operand usage

copy

public Expression copy(RebindingMap rebindings)

Description copied from class: Expression

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.

Returns:

the copy of the original expression

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.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

computeCardinality

public int computeCardinality()

Description copied from class: UnaryExpression

Determine the static cardinality. Default implementation returns the cardinality of the operand

Overrides:

computeCardinality in class UnaryExpression

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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

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.

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

mapItem

public Item mapItem(Item item)
             throws XPathException

Map one item to another item.

Specified by:

mapItem in interface ItemMappingFunction<Item<?>,Item<?>>

Parameters:

item - The input item to be mapped.

Returns:

either the output item, or null.

Throws:

XPathException - if a dynamic error occurs

isDeemedEmpty

public static boolean isDeemedEmpty(Item item)

Test whether an item is empty according to the definition in the spec for xsl:conditional-content

Parameters:

item - the item to be tested

Returns:

true if it is "empty", for example, an element without children

getExpressionName

public String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class Expression

Returns:

a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.

export

public void export(ExpressionPresenter out)
            throws XPathException

Description copied from class: UnaryExpression

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

Specified by:

export in interface ExportAgent

Overrides:

export in class UnaryExpression

Parameters:

out - the expression presenter used to display the structure

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

getStreamerName

public String getStreamerName()

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

Returns:

the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class