net.sf.saxon.expr.flwor

Class TupleExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.flwor.TupleExpression

All Implemented Interfaces:

ExportAgent, IdentityComparable

public class TupleExpression
extends Expression

A tuple expression is an expression that returns a tuple. Specifically, it is a list local variables references; it returns a Tuple item containg the current value of these variables.

Field Summary

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

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

Constructor Summary

Constructors

Constructor and Description
TupleExpression()

Method Summary

Modifier and Type	Method and Description
int	computeCardinality() Get the cardinality of the expression.
int	computeHashCode() Hashcode supporting equals()
Expression	copy(RebindingMap rebindings) Copy an expression.
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
Tuple	evaluateItem(XPathContext context) Evaluate an expression as a single item.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
java.lang.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().
int	getIntrinsicDependencies() Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
ItemType	getItemType() Determine the static item type of the expression, as precisely possible.
protected OperandArray	getOperanda() Get the data structure holding the operands of this expression.
int	getSize()
LocalVariableReference	getSlot(int i)
boolean	includesBinding(Binding binding)
java.lang.Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
void	setCurrentTuple(XPathContext context, Tuple tuple) Set the local variables in the current stack frame to values corresponding to a supplied tuple
protected void	setOperanda(OperandArray operanda) Set the data structure for the operands of this expression.
void	setSlot(int i, LocalVariableReference ref)
void	setVariables(java.util.List<LocalVariableReference> refs)
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform type checking of an expression and its subexpressions.

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isInstruction, isLiftable, isMultiThreaded, isSameExpression, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered, verifyParentPointers, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

TupleExpression

public TupleExpression()

Method Detail

setOperanda

protected void setOperanda(OperandArray operanda)

Set the data structure for the operands of this expression. This must be created during initialisation of the expression and must not be subsequently changed

Parameters:

operanda - the data structure for expression operands

getOperanda

protected OperandArray getOperanda()

Get the data structure holding the operands of this expression.

Returns:

the data structure holding expression operands

operands

public java.lang.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. Default implementation works off the results of iterateSubExpressions()

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

setVariables

public void setVariables(java.util.List<LocalVariableReference> refs)

getSize

public int getSize()

getSlot

public LocalVariableReference getSlot(int i)

setSlot

public void setSlot(int i,
                    LocalVariableReference ref)

includesBinding

public boolean includesBinding(Binding binding)

getItemType

public ItemType getItemType()

Description copied from class: Expression

Determine the static item type of the expression, as precisely 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)

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException

Description copied from class: Expression

Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

Overrides:

typeCheck in class Expression

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

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)

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

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class java.lang.Object

Parameters:

other - the expression to be compared with this one

Returns:

true if the two expressions are statically equivalent

computeHashCode

public int computeHashCode()

Hashcode supporting equals()

Overrides:

computeHashCode in class Expression

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings -

Returns:

the copy of the original expression

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.

evaluateItem

public Tuple evaluateItem(XPathContext context)
                   throws XPathException

Description copied from class: Expression

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

getExpressionName

public java.lang.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.

setCurrentTuple

public void setCurrentTuple(XPathContext context,
                            Tuple tuple)
                     throws XPathException

Set the local variables in the current stack frame to values corresponding to a supplied tuple

Parameters:

context - identifies the stack frame to be modified

tuple - the tuple containing the current values

Throws:

XPathException

computeCardinality

public int computeCardinality()

Get the cardinality of the expression. This is exactly one, in the sense that evaluating the TupleExpression returns a single tuple.

Specified by:

computeCardinality in class Expression

Returns:

the static cardinality - EXACTLY_ONE

getIntrinsicDependencies

public int getIntrinsicDependencies()

Description copied from class: Expression

Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:

getIntrinsicDependencies in class Expression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty