Implements the node comparison operators >>, <<, and is. More...

#include <qnodecomparison_p.h>

Inheritance diagram for QPatternist::NodeComparison:

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

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

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

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

virtual SequenceType::List	expectedOperandTypes () const

	NodeComparison (const Expression::Ptr &operand1, const QXmlNodeModelIndex::DocumentOrder op, const Expression::Ptr &operand2)

virtual QXmlNodeModelIndex::DocumentOrder	operatorID () const

virtual SequenceType::Ptr	staticType () const

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

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

virtual ItemType::Ptr	expectedContextItemType () const

	Expression ()

bool	has (const Property prop) const

bool	hasDependency (const Property prop) const

virtual ID	id () const

bool	is (const ID id) const

bool	isEvaluated () const

virtual ItemType::Ptr	newFocusType () const

virtual QList< QExplicitlySharedDataPointer< OptimizationPass > >	optimizationPasses () 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::Ptr	typeCheck (const StaticContext::Ptr &context, const SequenceType::Ptr &reqType)

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 ()

Static Public Functions
static QString	displayName (const QXmlNodeModelIndex::DocumentOrder op)

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

Private Types
enum	Result { Empty, True, False }

Private Functions
Result	evaluate (const DynamicContext::Ptr &context) const

Properties
const QXmlNodeModelIndex::DocumentOrder	m_op

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

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 the node comparison operators >>, <<, and is.

See also: XML Path Language (XPath) 2.0, 3.5.3 QXmlNodeModelIndex Comparisons

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

Definition at line 72 of file qnodecomparison_p.h.

Enumerations

◆ Result

enum QPatternist::NodeComparison::Result

private

Enumerator
Empty
True
False

Definition at line 110 of file qnodecomparison_p.h.

         {
             Empty,
             True,
             False
         };

Constructors and Destructors

◆ NodeComparison()

NodeComparison::NodeComparison	(	const Expression::Ptr &	operand1,
		const QXmlNodeModelIndex::DocumentOrder	op,
		const Expression::Ptr &	operand2
	)

Definition at line 55 of file qnodecomparison.cpp.

                                : PairContainer(operand1, operand2)
                                , m_op(op)
 {
     Q_ASSERT(op == QXmlNodeModelIndex::Precedes   ||
              op == QXmlNodeModelIndex::Follows    ||
              op == QXmlNodeModelIndex::Is);
 }

Functions

◆ accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 179 of file qnodecomparison.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

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

virtual

If any operator is the empty sequence, the NodeComparison rewrites into that, since the empty sequence is always the result in that case.

Reimplemented from QPatternist::Expression.

Definition at line 129 of file qnodecomparison.cpp.

 {
     const Expression::Ptr me(PairContainer::compress(context));
 
     if(me != this)
     /* We're already rewritten. */
         return me;
 
     if(m_operand1->staticType()->cardinality().isEmpty() ||
        m_operand2->staticType()->cardinality().isEmpty())
     {
         // TODO issue a warning in the @p context saying that one of the operands
         // were empty, and that the expression always result in the empty sequence
         // (which never is the intent, right?).
         return EmptySequence::create(this, context);
     }
 
     return Expression::Ptr(this);
 }

◆ displayName()

QString NodeComparison::displayName ( const QXmlNodeModelIndex::DocumentOrder op )

static

Determines the string representation for a node comparison operator.

Returns

"<<" if op is Precedes
">>" if op is Follows
"is" if op is Is

Definition at line 149 of file qnodecomparison.cpp.

 {
     switch(op)
     {
         case QXmlNodeModelIndex::Is:
             return QLatin1String("is");
         case QXmlNodeModelIndex::Precedes:
             return QLatin1String("<<");
         default:
         {
             Q_ASSERT(op == QXmlNodeModelIndex::Follows);
             return QLatin1String(">>");
         }
     }
 }

◆ evaluate()

NodeComparison::Result NodeComparison::evaluate ( const DynamicContext::Ptr & context ) const

inlineprivate

Definition at line 91 of file qnodecomparison.cpp.

Referenced by evaluateEBV(), and evaluateSingleton().

 {
     const Item op1(m_operand1->evaluateSingleton(context));
     if(!op1)
         return Empty;
 
     const Item op2(m_operand2->evaluateSingleton(context));
     if(!op2)
         return Empty;
 
     /* We just returns an arbitrary value, since there's no order defined for nodes from different
      * models, except for that the return value must be stable. */
     if(op1.asNode().model() != op2.asNode().model())
         return False;
 
     switch(m_op)
     {
         case QXmlNodeModelIndex::Is:
             return op1.asNode().is(op2.asNode()) ? True : False;
         case QXmlNodeModelIndex::Precedes:
             return op1.asNode().compareOrder(op2.asNode()) == QXmlNodeModelIndex::Precedes ? True : False;
         default:
         {
             Q_ASSERT(m_op == QXmlNodeModelIndex::Follows);
             return op1.asNode().compareOrder(op2.asNode()) == QXmlNodeModelIndex::Follows ? True : False;
         }
     }
 }

◆ evaluateEBV()

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

virtual

Determines the Effective Boolean Value of the expression.

The Effective Boolean Value of a value is not necessarily the same as converting the value to a new value of type xs:boolean.

Note that this function cannot return the empty sequence, evaluateSingleton() must be overridden in order to be able to do that.

The default implementation results in a type error. Hence, this function must be overridden if such behavior is not of interest.

See also: XML Path Language (XPath) 2.0, 2.4.3 Effective Boolean Value

Reimplemented from QPatternist::Expression.

Definition at line 79 of file qnodecomparison.cpp.

 {
     switch(evaluate(context))
     {
         case True:
             return true;
         default:
             /* We include the empty sequence here. */
             return false;
     }
 }

◆ evaluateSingleton()

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

virtual

Reimplemented from QPatternist::Expression.

Definition at line 66 of file qnodecomparison.cpp.

 {
     switch(evaluate(context))
     {
         case True:
             return CommonValues::BooleanTrue;
         case False:
             return CommonValues::BooleanFalse;
         default:
             return Item();
     }
 }

◆ expectedOperandTypes()

SequenceType::List NodeComparison::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 121 of file qnodecomparison.cpp.

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

◆ operatorID()

QXmlNodeModelIndex::DocumentOrder NodeComparison::operatorID ( ) const

virtual

Definition at line 174 of file qnodecomparison.cpp.

 {
     return m_op;
 }

◆ staticType()

SequenceType::Ptr NodeComparison::staticType ( ) const

virtual

Returns: either CommonSequenceTypes::ZeroOrOneBoolean or CommonSequenceTypes::ExactlyOneBoolean depending on the static cardinality of its operands.

Implements QPatternist::Expression.

Definition at line 165 of file qnodecomparison.cpp.

 {
     if(m_operand1->staticType()->cardinality().allowsEmpty() ||
        m_operand2->staticType()->cardinality().allowsEmpty())
         return CommonSequenceTypes::ZeroOrOneBoolean;
     else
         return CommonSequenceTypes::ExactlyOneBoolean;
 }

Properties

◆ m_op

const QXmlNodeModelIndex::DocumentOrder QPatternist::NodeComparison::m_op

private

Definition at line 118 of file qnodecomparison_p.h.

Referenced by evaluate(), and operatorID().

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

/src/xmlpatterns/expr/qnodecomparison_p.h
/src/xmlpatterns/expr/qnodecomparison.cpp

Public Functions

Static Public Functions

Private Types

Private Functions

Properties

Additional Inherited Members

Detailed Description

Enumerations

◆ Result

Constructors and Destructors

◆ NodeComparison()

Functions

◆ accept()

◆ compress()

◆ displayName()

◆ evaluate()

◆ evaluateEBV()

◆ evaluateSingleton()

◆ expectedOperandTypes()

◆ operatorID()

◆ staticType()

Properties

◆ m_op