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

public final 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

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
static class	AtomicSequenceConverter.UntypedConverter

Field Summary

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, 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

AtomicSequenceConverter(Expression sequence, PlainType requiredItemType, boolean allConverted)
Constructor

Method Summary

void	allocateConverter(Configuration config)
int	computeCardinality() Determine the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
Expression	copy() Copy an expression.
boolean	equals(Object other) Is this expression the same as another expression?
Item	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
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by the expression, if possible
int	hashCode() get HashCode for comparing two expressions.
boolean	isAllItemsConverted() Ask if all items in the input are converted to the target type
SequenceIterator	iterate(XPathContext context) Iterate over the sequence of values
static AtomicSequenceConverter	makeUntypedSequenceConverter(Configuration config, Expression operand, PlainType requiredItemType) Create an AtomicSequenceConverter that converts all untypedAtomic values in the input sequence to a specified target type, while leaving items other than untypedAtomic unchanged
static AtomicSequenceConverter	makeUntypedSequenceRejector(Configuration config, Expression operand, PlainType requiredItemType)
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

displayOperator, 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, getExpressionName, getHostLanguage, getImplementationMethod, 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, staticTypeCheck, suppressValidation, 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

Constructor Detail

AtomicSequenceConverter

public AtomicSequenceConverter(Expression sequence,
                               PlainType requiredItemType,
                               boolean allConverted)

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, using the rules for "cast as".

Method Detail

makeUntypedSequenceConverter

public static AtomicSequenceConverter makeUntypedSequenceConverter(Configuration config,
                                                                   Expression operand,
                                                                   PlainType requiredItemType)

Create an AtomicSequenceConverter that converts all untypedAtomic values in the input sequence to a specified target type, while leaving items other than untypedAtomic unchanged

Parameters:

config - the Saxon configuration

operand - the expression that delivers the input sequence

requiredItemType - the type to which untypedAtomic values should be cast, which must either be an atomic type or a "plain" union type

Returns:

an AtomicSequenceConverter that performs the required conversion

makeUntypedSequenceRejector

public static AtomicSequenceConverter makeUntypedSequenceRejector(Configuration config,
                                                                  Expression operand,
                                                                  PlainType requiredItemType)

allocateConverter

public void allocateConverter(Configuration config)

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)

isAllItemsConverted

public boolean isAllItemsConverted()

Ask if all items in the input are converted to the target type

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.

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

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 Item 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

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