Package com.saxonica.ee.update

Class CopyModifyExpression

java.lang.Object

net.sf.saxon.expr.Expression

com.saxonica.ee.update.CopyModifyExpression

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

public class CopyModifyExpression
extends Expression

A copy-modify expression (called a "transform" expression in the XQuery Update specification)

Note that this expression doesn't actually perform the copy. It gets wrapped in a let expression that does let $var := $input.copy-of().

Field Summary

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

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

Constructor Summary

Constructors

Constructor	Description
CopyModifyExpression(Expression updateExp, Expression returnExp, int validationMode)	Create a copy-modify expression (also known as a transform expresion)

Method Summary

Modifier and Type	Method	Description
void	checkForUpdatingSubexpressions()	Check to ensure that this expression does not contain any inappropriate updating subexpressions.
protected int	computeCardinality()	Determine the static cardinality of the expression.
Expression	copy(RebindingMap rebindings)	Copy an expression.
Item	evaluateItem(XPathContext context)	Evaluate an expression as a single item.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
Expression	getCopyBindings()
Elaborator	getElaborator()	Make an elaborator for this expression
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()	Determine the data type of the expression, if possible.
Expression	getReturnExp()
Expression	getUpdateExp()
boolean	isUpdatingExpression()	Determine whether this is an updating expression as defined in the XQuery update specification
SequenceIterator	iterate(XPathContext context)	Return an Iterator to iterate over the values of a sequence.
Iterable<Operand>	operands()	Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
void	process(Outputter output, XPathContext context)	Process the instruction, without returning any tail calls
void	setCopyBindings(Expression copyBindings)	Set the copy bindings.
void	setReturnExp(Expression returnExp)
void	setUpdateExp(Expression updateExp)

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkPermittedContents, computeDependencies, computeHashCode, computeSpecialProperties, computeStaticProperties, dispatchTailCall, dynamicError, effectiveBooleanValue, equals, evaluateAsString, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isVacuousExpression, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, toShortString, toString, typeCheck, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Constructor Details

CopyModifyExpression

public CopyModifyExpression(Expression updateExp,
 Expression returnExp,
 int validationMode)

Create a copy-modify expression (also known as a transform expresion)

Parameters:

updateExp - the expression appearing in the modify clause

returnExp - the expression appearing in the return clause

validationMode - the mode for validating the updated nodes (strict, lax, or skip)

Method Details

operands

public Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

getUpdateExp

public Expression getUpdateExp()

setUpdateExp

public void setUpdateExp(Expression updateExp)

getReturnExp

public Expression getReturnExp()

setReturnExp

public void setReturnExp(Expression returnExp)

getCopyBindings

public Expression getCopyBindings()

setCopyBindings

public void setCopyBindings(Expression copyBindings)

Set the copy bindings. This is an expression whose value is the set of nodes that are allowed to be updated. Normally it will consist of a variable reference or a sequence of variable references.

Parameters:

copyBindings - the set of Let expressions that bind variables that were copied during the copy phase and that therefore may be updated during the modify phase

computeCardinality

protected int computeCardinality()

Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

Specified by:

computeCardinality in class Expression

Returns:

one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

getItemType

public ItemType getItemType()

Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Specified by:

getItemType in class Expression

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

isUpdatingExpression

public boolean isUpdatingExpression()

Determine whether this is an updating expression as defined in the XQuery update specification

Overrides:

isUpdatingExpression in class Expression

Returns:

false: although this expression performs updates, it is not classified as an updating expression

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.

checkForUpdatingSubexpressions

public void checkForUpdatingSubexpressions()
                                    throws XPathException

Check to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.

Overrides:

checkForUpdatingSubexpressions in class Expression

Throws:

XPathException - if the expression has a non-permitted updating subexpression

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - variables to be rebound

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

export

public void export(ExpressionPresenter out)
            throws XPathException

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

Specified by:

export in interface ExportAgent

Specified by:

export in class Expression

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.

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. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

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 an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.

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

process

public void process(Outputter output,
 XPathContext context)
             throws XPathException

Process the instruction, without returning any tail calls

Overrides:

process in class Expression

Parameters:

output - the destination for the result

context - The dynamic context, giving access to the current node,

Throws:

XPathException - if a dynamic error occurs

getElaborator

public Elaborator getElaborator()

Make an elaborator for this expression

Overrides:

getElaborator in class Expression

Returns:

an appropriate Elaborator