net.sf.saxon.expr
Class SuppliedParameterReference

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.SuppliedParameterReference

All Implemented Interfaces:

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

public class SuppliedParameterReference
extends Expression

Supplied parameter reference: this is an internal expression used to refer to the value of the n'th parameter supplied on a template call (apply-templates). It is used within a type-checking expression designed to check the consistency of the supplied value with the required type. This type checking is all done at run-time, because the binding of apply-templates to actual template rules is entirely dynamic.

See Also:

Serialized Form

Field Summary

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

SuppliedParameterReference(int slot)
Constructor

Method Summary

int	computeCardinality() Get the static cardinality
Expression	copy() Copy an expression.
Item	evaluateItem(XPathContext context) Evaluate an expression as a single item.
ValueRepresentation	evaluateVariable(XPathContext c) Get the value of this expression in a given context.
void	explain(ExpressionPresenter destination) Diagnostic print of expression structure.
int	getIntrinsicDependencies() Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the expression, if possible.
SequenceIterator	iterate(XPathContext context) Get the value of this expression in a given context.
Expression	optimize(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
void	setSuppliedType(SequenceType type) Set the type of the supplied value if known
String	toString() The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
Expression	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Perform type checking of an expression and its subexpressions.

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, iterateSubExpressions, markTailFunctionCalls, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SuppliedParameterReference

public SuppliedParameterReference(int slot)

Constructor

Parameters:

slot - identifies this parameter. The value -1 indicates that the value is to be obtained from the dynamic stack held in the context object.

Method Detail

setSuppliedType

public void setSuppliedType(SequenceType type)

Set the type of the supplied value if known

Parameters:

type - of the supplied value

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     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.

If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:

typeCheck in class Expression

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

Description copied from class: Expression

Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

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 Expression

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)

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression, if possible.

Specified by:

getItemType in class Expression

Parameters:

th - the type hierarchy cache

Returns:

Type.ITEM, because we don't know the type of the supplied value in advance.

getIntrinsicDependencies

public int getIntrinsicDependencies()

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

computeCardinality

public int computeCardinality()

Get the static cardinality

Specified by:

computeCardinality in class Expression

Returns:

ZERO_OR_MORE, unless we know the type of the supplied value in advance.

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

evaluateVariable

public ValueRepresentation evaluateVariable(XPathContext c)
                                     throws XPathException

Get the value of this expression in a given context.

Parameters:

c - the XPathContext which contains the relevant variable bindings

Returns:

the value of the variable, if it is defined

Throws:

XPathException - if the variable is undefined

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Get the value of this expression in a given context.

Specified by:

iterate in interface SequenceIterable

Overrides:

iterate in class Expression

Parameters:

context - the XPathContext which contains the relevant variable bindings

Returns:

the value of the variable, if it is defined

Throws:

XPathException - if the variable is undefined

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.

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 destination)

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

Specified by:

explain in class Expression

Parameters:

destination - the expression presenter used to display the structure

toString

public String toString()

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:

toString in class Expression

Returns:

a representation of the expression as a string