net.sf.saxon.expr
Class UntypedAtomicConverter

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.UnaryExpression
          net.sf.saxon.expr.UntypedAtomicConverter

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public final class UntypedAtomicConverter
extends UnaryExpression

An UntypedAtomicConverter is an expression that converts any untypedAtomic items in a sequence to a specified type

See Also:

Serialized Form

Field Summary

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

operand

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

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

UntypedAtomicConverter(Expression sequence, AtomicType requiredItemType, boolean allConverted, RoleLocator role)
Constructor

Method Summary

boolean	areAllItemsConverted() Determine whether all items are to be converted, or only the subset that are untypedAtomic
int	computeCardinality() Determine the static cardinality.
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
Item	evaluateItem(XPathContext context) Evaluate as an Item.
void	explain(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().
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by the expression
ItemMappingFunction	getMappingFunction(XPathContext context) Get the mapping function that converts untyped atomic values to the required type
ItemType	getRequiredItemType() Get the item type to which untyped atomic items must be converted
SequenceIterator	iterate(XPathContext context) Iterate over the sequence of values
Expression	optimize(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
Expression	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Type-check the expression

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

equals, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression, simplify, 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, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

UntypedAtomicConverter

public UntypedAtomicConverter(Expression sequence,
                              AtomicType requiredItemType,
                              boolean allConverted,
                              RoleLocator role)

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 untypedAtomic items in the sequence should be converted, using the rules for "cast as".

allConverted - true if the result of this expression is a sequence in which all items belong to the required type

role - Diagnostic information for use if conversion fails

Method Detail

getRequiredItemType

public ItemType getRequiredItemType()

Get the item type to which untyped atomic items must be converted

Returns:

the required item type

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

areAllItemsConverted

public boolean areAllItemsConverted()

Determine whether all items are to be converted, or only the subset that are untypedAtomic

Returns:

true if all items are to be converted

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the items returned by the expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th - the type hierarchy cache

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

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

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType 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,
                           ItemType contextItemType)
                    throws XPathException

Perform optimisation of an expression and its subexpressions.

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 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.

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 iterate(XPathContext context)
                         throws XPathException

Iterate over the sequence of values

Specified by:

iterate in interface SequenceIterable

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

getMappingFunction

public ItemMappingFunction getMappingFunction(XPathContext context)

Get the mapping function that converts untyped atomic values to the required type

Parameters:

context - the dynamic evaluation context for the conversion

Returns:

the mapping function

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

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

Specified by:

evaluateItem in interface EvaluableItem

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

explain

public void explain(ExpressionPresenter out)

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

Overrides:

explain in class UnaryExpression

Parameters:

out - the expression presenter used to display the structure

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

Returns:

the operator, as a string

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.