net.sf.saxon.expr

Class AtomicSequenceConverter

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.AtomicSequenceConverter

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

Direct Known Subclasses:

UntypedSequenceConverter

public class AtomicSequenceConverter
extends UnaryExpression

An AtomicSequenceConverter is an expression that performs a cast on each member of a supplied sequence

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AtomicSequenceConverter.AtomicSequenceMappingFunction Mapping function wrapped around a converter
static class	AtomicSequenceConverter.ToStringMappingFunction Mapping function that converts every item in a sequence to a string

Field Summary

Fields

Modifier and Type	Field and Description
protected Converter	converter
static AtomicSequenceConverter.ToStringMappingFunction	TO_STRING_MAPPER

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

operand

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
AtomicSequenceConverter(Expression sequence, PlainType requiredItemType) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
void	allocateConverter(Configuration config, boolean allowNull)
int	computeCardinality() Determine the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
Expression	copy() Copy an expression.
protected String	displayOperator(Configuration config) Give a string representation of the operator for use in diagnostics
boolean	equals(Object other) Is this expression the same as another expression?
AtomicValue	evaluateItem(XPathContext context) Evaluate as an Item.
void	explain(ExpressionPresenter destination) Diagnostic print of expression structure.
Converter	getConverter() Get the converter used to convert the items in the sequence
ExpressionCompiler	getExpressionCompiler() Return the compiler of the expression
String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by the expression, if possible
PlainType	getRequiredItemType() Get the required item type (the target type of the conversion
int	getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons) Get the "sweep" of this expression as defined in the W3C streamability specifications.
AtomicSequenceConverterAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
int	hashCode() get HashCode for comparing two expressions.
SequenceIterator<? extends AtomicValue>	iterate(XPathContext context) Iterate over the sequence of values
Expression	optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.
void	setConverter(Converter converter)
Expression	simplify(ExpressionVisitor visitor) Simplify an expression
Expression	typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expression

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

getBaseExpression, iterateSubExpressions, promote, replaceSubExpression, toString

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSubExpressionInfo, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError

Methods inherited from class java.lang.Object

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

Field Detail

TO_STRING_MAPPER

public static AtomicSequenceConverter.ToStringMappingFunction TO_STRING_MAPPER

converter

protected Converter converter

Constructor Detail

AtomicSequenceConverter

public AtomicSequenceConverter(Expression sequence,
                       PlainType requiredItemType)

Constructor

Parameters:

sequence - this must be a sequence of atomic values. This is not checked; a ClassCastException will occur if the precondition is not satisfied.

requiredItemType - the item type to which all items in the sequence should be converted,

Method Detail

allocateConverter

public void allocateConverter(Configuration config,
                     boolean allowNull)

getRequiredItemType

public PlainType getRequiredItemType()

Get the required item type (the target type of the conversion

Returns:

the required item type

getConverter

public Converter getConverter()

Get the converter used to convert the items in the sequence

Returns:

the converter. Note that a converter is always allocated during the typeCheck() phase, even if the source type is not known.

setConverter

public void setConverter(Converter converter)

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Simplify an expression

Overrides:

simplify in class UnaryExpression

Parameters:

visitor - an expression visitor

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

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

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)

optimize

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

Perform optimisation of an expression and its subexpressions.

Overrides:

optimize in class UnaryExpression

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)

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NON_CREATIVE.

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 AtomicSequenceConverterAdjunct 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

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

iterate

public SequenceIterator<? extends AtomicValue> iterate(XPathContext context)
                                                throws XPathException

Iterate over the sequence of values

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

evaluateItem

public AtomicValue evaluateItem(XPathContext context)
                         throws XPathException

Evaluate as an Item. This should only be called if the AtomicSequenceConverter has cardinality zero-or-one

Overrides:

evaluateItem in class Expression

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the items returned by the expression, if possible

Overrides:

getItemType in class UnaryExpression

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 in advance)

computeCardinality

public int computeCardinality()

Determine the static cardinality of the expression

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

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

hashCode

public int hashCode()

get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

Overrides:

hashCode in class UnaryExpression

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

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 explain() output displaying the expression.

displayOperator

protected String displayOperator(Configuration config)

Description copied from class: UnaryExpression

Give a string representation of the operator for use in diagnostics

Overrides:

displayOperator in class UnaryExpression

Parameters:

config - the Saxon configuration

Returns:

the operator, as a string

explain

public void explain(ExpressionPresenter destination)

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

Overrides:

explain in class UnaryExpression

Parameters:

destination - the expression presenter used to display the structure