net.sf.saxon.expr
Class Atomizer

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.UnaryExpression
          net.sf.saxon.expr.Atomizer

All Implemented Interfaces:

Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

public final class Atomizer
extends UnaryExpression

An Atomizer is an expression corresponding essentially to the fn:data() function: it maps a sequence by replacing nodes with their typed values

See Also:

Serialized Form

Nested Class Summary

static class

Atomizer.AtomizingFunction Implement the mapping function.

Field Summary

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

operand

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

locationId, staticProperties

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Atomizer(Expression sequence, Configuration config)
Constructor

Method Summary

int	computeCardinality() Determine the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
protected String	displayOperator(NamePool pool) Give a string representation of the operator for use in diagnostics
Item	evaluateItem(XPathContext context) Evaluate as an Item.
static ItemType	getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th) Compute the type that will result from atomizing the result of a given expression
ItemType	getItemType(TypeHierarchy th) Determine the data type of the items returned by the expression, if possible
SequenceIterator	iterate(XPathContext context) Iterate over the sequence of values
Expression	simplify(StaticContext env) Simplify an expression
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

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

display, equals, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

Atomizer

public Atomizer(Expression sequence,
                Configuration config)

Constructor

Parameters:

sequence - the sequence to be atomized

config - the Configuration. Used only for optimization, may be null. Atomization is faster if it is known in advance that all nodes will be untyped.

Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify an expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class UnaryExpression

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression

Specified by:

typeCheck in interface Expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

env - the static context of the expression

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:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NON_CREATIVE.

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the sequence of values

Specified by:

iterate in interface Expression

Overrides:

iterate in class ComputedExpression

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 Atomizer has cardinality zero-or-one, which will only be the case if the underlying expression has cardinality zero-or-one.

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the result is always an atomic type, but it might be more specific.

getAtomizedItemType

public static final ItemType getAtomizedItemType(Expression operand,
                                                 boolean alwaysUntyped,
                                                 TypeHierarchy th)

Compute the type that will result from atomizing the result of a given expression

Parameters:

operand - the given expression

alwaysUntyped - true if it is known that nodes will always be untyped

Returns:

the item type of the result of evaluating the operand expression, after atomization

computeCardinality

public int computeCardinality()

Determine the static cardinality of the expression

Overrides:

computeCardinality in class UnaryExpression

displayOperator

protected String displayOperator(NamePool pool)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Returns:

the operator, as a string