Implements XPath 2.0's for expression. More...

#include <qforclause_p.h>

Inheritance diagram for QPatternist::ForClause:

Public Functions
virtual ExpressionVisitorResult::Ptr	accept (const ExpressionVisitor::Ptr &visitor) const

virtual Expression::Ptr	compress (const StaticContext::Ptr &context)

virtual Item::Iterator::Ptr	evaluateSequence (const DynamicContext::Ptr &context) const

virtual Item	evaluateSingleton (const DynamicContext::Ptr &context) const

virtual void	evaluateToSequenceReceiver (const DynamicContext::Ptr &context) const

virtual SequenceType::List	expectedOperandTypes () const

	ForClause (const VariableSlotID varSlot, const Expression::Ptr &bindingSequence, const Expression::Ptr &returnExpression, const VariableSlotID positionSlot)

virtual ID	id () const

Item	mapToItem (const Item &item, const DynamicContext::Ptr &context) const

Item::Iterator::Ptr	mapToSequence (const Item &item, const DynamicContext::Ptr &context) const

virtual QList< QExplicitlySharedDataPointer< OptimizationPass > >	optimizationPasses () const

virtual SequenceType::Ptr	staticType () const

virtual Expression::Ptr	typeCheck (const StaticContext::Ptr &context, const SequenceType::Ptr &reqType)

Public Functions inherited from QPatternist::PairContainer
virtual bool	compressOperands (const StaticContext::Ptr &)

virtual Expression::List	operands () const

virtual void	setOperands (const Expression::List &operands)

Public Functions inherited from QPatternist::Expression
virtual const SourceLocationReflection *	actualReflection () const
	Returns `this`. More...

virtual void	announceFocusType (const ItemType::Ptr &itemType)

Properties	deepProperties () const
	Computes the union of properties for this Expression and all its descending children. More...

virtual Properties	dependencies () const

virtual QString	description () const

virtual bool	evaluateEBV (const DynamicContext::Ptr &context) const

virtual ItemType::Ptr	expectedContextItemType () const

	Expression ()

bool	has (const Property prop) const

bool	hasDependency (const Property prop) const

bool	is (const ID id) const

bool	isEvaluated () const

virtual ItemType::Ptr	newFocusType () const

virtual PatternPriority	patternPriority () const

virtual Properties	properties () const

const Expression::Ptr &	rewrite (const Expression::Ptr &to, const StaticContext::Ptr &context) const
	Rewrites this Expression to `to`, and return `to`. More...

virtual	~Expression ()

Public Functions inherited from QSharedData
	QSharedData ()
	Constructs a QSharedData object with a reference count of 0. More...

	QSharedData (const QSharedData &)
	Constructs a QSharedData object with reference count 0. More...

Public Functions inherited from QPatternist::CppCastingHelper< Expression >
const TCastTarget *	as () const

TCastTarget *	as ()

Public Functions inherited from QPatternist::SourceLocationReflection
virtual QSourceLocation	sourceLocation () const

	SourceLocationReflection ()

virtual	~SourceLocationReflection ()

Private Types
typedef QExplicitlySharedDataPointer< const ForClause >	ConstPtr

Private Functions
void	riggPositionalVariable (const DynamicContext::Ptr &context, const Item::Iterator::Ptr &source) const

Properties
bool	m_allowsMany

const VariableSlotID	m_positionSlot

const VariableSlotID	m_varSlot

Additional Inherited Members
Public Types inherited from QPatternist::Expression
typedef QExplicitlySharedDataPointer< const Expression >	ConstPtr
	A smart pointer wrapping `const` Expression instances. More...

enum	ID { IDBooleanValue = 1, IDCountFN, IDEmptyFN, IDExistsFN, IDExpressionSequence, IDGeneralComparison, IDIfThenClause, IDIgnorableExpression, IDIntegerValue, IDPositionFN, IDStringValue, IDValueComparison, IDRangeVariableReference, IDContextItem, IDUserFunctionCallsite, IDExpressionVariableReference, IDAttributeConstructor, IDUpperCaseFN, IDLowerCaseFN, IDFirstItemPredicate, IDEmptySequence, IDReturnOrderBy, IDLetClause, IDForClause, IDPath, IDNamespaceConstructor, IDArgumentReference, IDGenericPredicate, IDAxisStep, IDFloat, IDCombineNodes, IDUnresolvedVariableReference, IDCardinalityVerifier }

typedef QList< Expression::Ptr >	List

typedef QFlags< Property >	Properties

enum	Property { UseContextItem = 1, DisableElimination = 1 << 1, IsEvaluated = 1 << 2, DisableTypingDeduction = 1 << 3, EmptynessFollowsChild = 1 << 4, RewriteToEmptyOnEmpty = 1 << 5, RequiresFocus = 1 << 6, AffectsOrderOnly = 1 << 7, RequiresContextItem = (1 << 8) \| RequiresFocus, CreatesFocusForLast = 1 << 9, LastOperandIsCollation = 1 << 10, DependsOnLocalVariable = (1 << 11) \| DisableElimination, EvaluationCacheRedundant = (1 << 12), IsNodeConstructor = 1 << 13, RequiresCurrentItem = 1 << 14 }

typedef QExplicitlySharedDataPointer< Expression >	Ptr
	A smart pointer wrapping mutable Expression instances. More...

typedef ::QAbstractXmlForwardIterator< Expression::Ptr >	QAbstractXmlForwardIterator

typedef QVector< Expression::Ptr >	Vector

Static Public Functions inherited from QPatternist::Expression
static void	rewrite (Expression::Ptr &old, const Expression::Ptr &New, const StaticContext::Ptr &context)

Public Variables inherited from QSharedData
QAtomicInt	ref

Protected Functions inherited from QPatternist::PairContainer
	PairContainer (const Expression::Ptr &operand1, const Expression::Ptr &operand2)

Protected Functions inherited from QPatternist::Expression
void	typeCheckOperands (const StaticContext::Ptr &context)

Protected Functions inherited from QPatternist::CppCastingHelper< Expression >
	CppCastingHelper ()

Protected Variables inherited from QPatternist::PairContainer
Expression::Ptr	m_operand1

Expression::Ptr	m_operand2

Detailed Description

Implements XPath 2.0's for expression.

See also: XML Path Language (XPath) 2.0, 3.7 For Expressions

Author: Frans Englich frans.nosp@m..eng.nosp@m.lich@.nosp@m.noki.nosp@m.a.com

Definition at line 72 of file qforclause_p.h.

Typedefs

◆ ConstPtr

typedef QExplicitlySharedDataPointer<const ForClause> QPatternist::ForClause::ConstPtr

private

Definition at line 108 of file qforclause_p.h.

Constructors and Destructors

◆ ForClause()

ForClause::ForClause	(	const VariableSlotID	varSlot,
		const Expression::Ptr &	bindingSequence,
		const Expression::Ptr &	returnExpression,
		const VariableSlotID	positionSlot
	)

If positionSlot is -1, no positional variable will be used.

Definition at line 55 of file qforclause.cpp.

                                                         : PairContainer(bindingSequence, returnExpression),
                                                           m_varSlot(varSlot),
                                                           m_positionSlot(positionSlot),
                                                           m_allowsMany(true)
 {
     Q_ASSERT(m_positionSlot > -2);
 }

Functions

◆ accept()

ExpressionVisitorResult::Ptr ForClause::accept ( const ExpressionVisitor::Ptr & visitor ) const

virtual

Implements QPatternist::Expression.

Definition at line 185 of file qforclause.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

Expression::Ptr ForClause::compress ( const StaticContext::Ptr & context )

virtual

Sets m_allowsMany properly.

Reimplemented from QPatternist::Expression.

Definition at line 151 of file qforclause.cpp.

 {
     const Expression::Ptr me(PairContainer::compress(context));
     if(me != this)
         return me;
 
     /* This is done after calling PairContainer::typeCheck(). The advantage of this is that
      * m_allowsMany is updated according to what the operand says after it has compressed. However,
      * if it was initialized to false(as it once was..), ForClause::evaluateSequence()
      * would potentially have been called by PairContainer::compress(), and it would have
      * used an unsafe branch. */
     m_allowsMany = m_operand2->staticType()->cardinality().allowsMany();
 
     return me;
 }

◆ evaluateSequence()

Item::Iterator::Ptr ForClause::evaluateSequence ( const DynamicContext::Ptr & context ) const

virtual

Evaluate this Expression by iterating over it. This is a central function for evaluating expressions.

Expressions must always always return a valid QAbstractXmlForwardIterator and may never return 0. If an empty result is of interest to be returned, the EmptyIterator should be returned.

The default implementation returns a SingletonIterator over the item returned from evaluateSingleton().

Note: This function may raise an exception when calling, not only when QAbstractXmlForwardIterator::next() is called on the return value. This is because in some cases evaluateSingleton() is called directly.

Reimplemented from QPatternist::Expression.

Definition at line 87 of file qforclause.cpp.

Referenced by evaluateSingleton().

 {
     const Item::Iterator::Ptr source(m_operand1->evaluateSequence(context));
 
     riggPositionalVariable(context, source);
 
     if(m_allowsMany)
     {
         return makeSequenceMappingIterator<Item>(ConstPtr(this),
                                                  source,
                                                  context);
     }
     else
     {
         return makeItemMappingIterator<Item>(ConstPtr(this),
                                              source,
                                              context);
     }
 }

◆ evaluateSingleton()

Item ForClause::evaluateSingleton ( const DynamicContext::Ptr & context ) const

virtual

Reimplemented from QPatternist::Expression.

Definition at line 107 of file qforclause.cpp.

 {
     return evaluateSequence(context)->next();
 }

◆ evaluateToSequenceReceiver()

void ForClause::evaluateToSequenceReceiver ( const DynamicContext::Ptr & context ) const

virtual

Evaluates this Expression by sending its output to DynamicContext::outputReceiver().

Reimplemented from QPatternist::Expression.

Definition at line 112 of file qforclause.cpp.

 {
     Item::Iterator::Ptr it;
     const Item::Iterator::Ptr source(m_operand1->evaluateSequence(context));
 
     riggPositionalVariable(context, source);
 
     Item next(source->next());
 
     while(next)
     {
         context->setRangeVariable(m_varSlot, next);
         m_operand2->evaluateToSequenceReceiver(context);
         next = source->next();
     }
 }

◆ expectedOperandTypes()

SequenceType::List ForClause::expectedOperandTypes ( ) const

virtual

Returns a list of Sequence Types, describing the type of each of the expression's operands. Hence, this function has a relationship to the operands() function:

- The lengths of the lists returned by expectedOperandTypes()
and operands() should always be equal in length, since one
cannot describe the type of a non-existent operand(and all
operands must have type information).
- A significant difference between the two functions is that while
the type of objects in the list returned by operands() may vary
between compilations/static context, simply because the particular
Expression is part of different XPath expressions, the
types in the list returned by expectedOperandTypes is always the same
since the function/operator signature never changes.

This function should not be confused with staticType(), which returns the static type of the expression itself, not its operands. The function call is an expression where this is clear: the type of the return value is not the same as the arguments' types. The static type of the operands supplied to the expression can be determined via the staticType() function of the instances returned by operands().

If the expression has no operands, an empty list should be returned.

Implements QPatternist::Expression.

Definition at line 177 of file qforclause.cpp.

 {
     SequenceType::List result;
     result.append(CommonSequenceTypes::ZeroOrMoreItems);
     result.append(CommonSequenceTypes::ZeroOrMoreItems);
     return result;
 }

◆ id()

Expression::ID ForClause::id ( ) const

virtual

This property, which has no setter, returns an enum value that uniquely identifies this Expression. Patternist makes no use of C++'s dynamic_cast feature, but uses this polymorphic function instead.

Returns: always IgnorableExpression.

Reimplemented from QPatternist::Expression.

Definition at line 195 of file qforclause.cpp.

 {
     return IDForClause;
 }

◆ mapToItem()

Item ForClause::mapToItem	(	const Item &	item,
		const DynamicContext::Ptr &	context
	)		const

inline

Definition at line 66 of file qforclause.cpp.

 {
     context->setRangeVariable(m_varSlot, item);
     return m_operand2->evaluateSingleton(context);
 }

◆ mapToSequence()

Item::Iterator::Ptr ForClause::mapToSequence	(	const Item &	item,
		const DynamicContext::Ptr &	context
	)		const

inline

Definition at line 73 of file qforclause.cpp.

 {
     context->setRangeVariable(m_varSlot, item);
     return m_operand2->evaluateSequence(context);
 }

◆ optimizationPasses()

OptimizationPass::List ForClause::optimizationPasses ( ) const

virtual

Returns the OptimizationPasses that applies for this Expression. The default implementation returns an empty list. Sub-classes can re-implement this function and return actual OptimizationPasses.

Returns: always an empty list.

Reimplemented from QPatternist::Expression.

Definition at line 190 of file qforclause.cpp.

 {
     return OptimizationPasses::forPasses;
 }

◆ riggPositionalVariable()

void ForClause::riggPositionalVariable	(	const DynamicContext::Ptr &	context,
		const Item::Iterator::Ptr &	source
	)		const

inlineprivate

Definition at line 80 of file qforclause.cpp.

Referenced by evaluateSequence(), and evaluateToSequenceReceiver().

 {
     if(m_positionSlot > -1)
         context->setPositionIterator(m_positionSlot, source);
 }

◆ staticType()

SequenceType::Ptr ForClause::staticType ( ) const

virtual

Returns: the static type of this Expression. For example, an 'and' expression have as static type xs:boolean

Implements QPatternist::Expression.

Definition at line 167 of file qforclause.cpp.

 {
     const SequenceType::Ptr returnType(m_operand2->staticType());
 
     return makeGenericSequenceType(returnType->itemType(),
                                    m_operand1->staticType()->cardinality()
                                         * /* multiply operator */
                                    returnType->cardinality());
 }

◆ typeCheck()

Expression::Ptr ForClause::typeCheck	(	const StaticContext::Ptr &	context,
		const SequenceType::Ptr &	reqType
	)

virtual

This implementation guarantees to never rewrite away this Expression, but at most rewrite it as a child of another expression(that presumably have a type checking role). It is therefore always safe to override this function and call this implementation and not worry about that this Expression becomes deleted.

Many Expressions override typeCheck() and performs optimizations, as opposed to doing it in the compress() stage. This is due to that the design of those Expressions often are tied to that certain simplifications are done at the typeCheck() stage of the compilation process or that it in some other way is related to what the typeCheck() do. Also, the earlier the AST can be simplified, the better the chances are for subsequent optimizations.

It is important that the super class's typeCheck() is called before doing any custom type checking, since the call can change the children(notably, the childrens' static types). For example, if the Expression, MyExpression in the example, does not match the required type, typeCheck returns the Expression wrapped in for example ItemVerifier, CardinalityVerifier, or both.

typeCheck() may be called many times. typeCheck() must either raise an error if this Expression is an invalid expression. Thus, it is guaranteed that an Expression is valid after typeCheck() is called.

Parameters

context	supplies information, such as namespace bindings and available function signatures, that can be needed at compilation time. `context` is guaranteed by the caller to never null.
reqType	the static type that this Expression must match when evaluated. `reqType` is guaranteed by the caller to never null.

Returns: an Expression that can be this Expression, or another expression, which somehow is necessary for making this Expression conforming to reqType

Reimplemented from QPatternist::Expression.

Definition at line 129 of file qforclause.cpp.

 {
     const Expression::Ptr me(PairContainer::typeCheck(context, reqType));
     const Cardinality card(m_operand1->staticType()->cardinality());
 
     /* If our source is empty we will always evaluate to the empty sequence, so rewrite. */
     if(card.isEmpty())
         return EmptySequence::create(this, context);
     else
         return me;
 
     /* This breaks because  the variable references haven't rewritten themselves, so
      * they dangle. When this is fixed, evaluateSingleton can be removed. */
     /*
     else if(card->allowsMany())
         return me;
     else
         return m_operand2;
         */
 }

Properties

◆ m_allowsMany

bool QPatternist::ForClause::m_allowsMany

private

Initialized to false. This default is always safe.

Definition at line 114 of file qforclause_p.h.

Referenced by compress(), and evaluateSequence().

◆ m_positionSlot

const VariableSlotID QPatternist::ForClause::m_positionSlot

private

Definition at line 110 of file qforclause_p.h.

Referenced by ForClause(), and riggPositionalVariable().

◆ m_varSlot

const VariableSlotID QPatternist::ForClause::m_varSlot

private

Definition at line 109 of file qforclause_p.h.

Referenced by evaluateToSequenceReceiver(), mapToItem(), and mapToSequence().

The documentation for this class was generated from the following files:

/src/xmlpatterns/expr/qforclause_p.h
/src/xmlpatterns/expr/qforclause.cpp

Public Functions

Private Types

Private Functions

Properties

Additional Inherited Members

Detailed Description

Typedefs

◆ ConstPtr

Constructors and Destructors

◆ ForClause()

Functions

◆ accept()

◆ compress()

◆ evaluateSequence()

◆ evaluateSingleton()

◆ evaluateToSequenceReceiver()

◆ expectedOperandTypes()

◆ id()

◆ mapToItem()

◆ mapToSequence()

◆ optimizationPasses()

◆ riggPositionalVariable()

◆ staticType()

◆ typeCheck()

Properties

◆ m_allowsMany

◆ m_positionSlot

◆ m_varSlot