Implements XPath 2.0 value comparions, such as the eq operator. More...

#include <qvaluecomparison_p.h>

Inheritance diagram for QPatternist::ValueComparison:

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

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

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

virtual SequenceType::List	expectedOperandTypes () const

virtual ID	id () const

AtomicComparator::Operator	operatorID () const

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

virtual SequenceType::Ptr	staticType () const

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

	ValueComparison (const Expression::Ptr &op1, const AtomicComparator::Operator op, const Expression::Ptr &op2)

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 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

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 ()

Static Public Functions
static bool	isCaseInsensitiveCompare (Expression::Ptr &op1, Expression::Ptr &op2)

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

Properties
const AtomicComparator::Operator	m_operator

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 Functions inherited from QPatternist::ComparisonPlatform< ValueComparison, true >
const AtomicComparator::Ptr &	comparator () const

bool	compare (const Item &i1, const Item &i2, const AtomicComparator::Ptr &comp, const AtomicComparator::Operator op) const
	Compares `i1` and `i2` with operator `op`, using comparator `comp`. All input arguments must be valid, and not `null`. More...

	ComparisonPlatform ()

AtomicComparator::ComparisonResult	detailedFlexibleCompare (const Item &it1, const Item &it2, const DynamicContext::Ptr &context) const
	like flexibleCompare(), but returns the result as an AtomicComparator::Operator instead of `bool`. More...

AtomicComparator::Ptr	fetchComparator (const ItemType::Ptr &type1, const ItemType::Ptr &type2, const ReportContext::Ptr &context) const

bool	flexibleCompare (const Item &it1, const Item &it2, const DynamicContext::Ptr &context) const
	Compares `it1` against `it2`, using comparator() and operatorID(). More...

void	prepareComparison (const AtomicComparator::Ptr &comparator)

void	useCaseInsensitiveComparator ()

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

Expression::Ptr	m_operand2

Detailed Description

Implements XPath 2.0 value comparions, such as the eq operator.

ComparisonPlatform is inherited with protected scope because ComparisonPlatform must access members of ValueComparison.

See also: XML Path Language (XPath) 2.0, 3.5.1 Value Comparisons

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

Definition at line 77 of file qvaluecomparison_p.h.

Constructors and Destructors

◆ ValueComparison()

ValueComparison::ValueComparison	(	const Expression::Ptr &	op1,
		const AtomicComparator::Operator	op,
		const Expression::Ptr &	op2
	)

Definition at line 55 of file qvaluecomparison.cpp.

                                                            : PairContainer(op1, op2),
                                                                m_operator(op)
 {
 }

Functions

◆ accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 153 of file qvaluecomparison.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

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

virtual

Overridden to optimize case-insensitive compares.

Reimplemented from QPatternist::Expression.

Definition at line 97 of file qvaluecomparison.cpp.

 {
     const Expression::Ptr me(PairContainer::compress(context));
 
     if(me != this)
         return me;
 
     if(isCaseInsensitiveCompare(m_operand1, m_operand2))
         useCaseInsensitiveComparator();
 
     return me;
 }

◆ evaluateSingleton()

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

virtual

Reimplemented from QPatternist::Expression.

Definition at line 62 of file qvaluecomparison.cpp.

 {
     const Item it1(m_operand1->evaluateSingleton(context));
     if(!it1)
         return Item();
 
     const Item it2(m_operand2->evaluateSingleton(context));
     if(!it2)
         return Item();
 
     return Boolean::fromValue(flexibleCompare(it1, it2, context));
 }

◆ expectedOperandTypes()

SequenceType::List ValueComparison::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 136 of file qvaluecomparison.cpp.

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

◆ id()

Expression::ID ValueComparison::id ( ) const

virtual

Returns: IDValueComparison

Reimplemented from QPatternist::Expression.

Definition at line 158 of file qvaluecomparison.cpp.

 {
     return IDValueComparison;
 }

◆ isCaseInsensitiveCompare()

bool ValueComparison::isCaseInsensitiveCompare	(	Expression::Ptr &	op1,
		Expression::Ptr &	op2
	)

static

It is considered that the string value from op1 will be compared against op2. This function determines whether the user intends the comparison to be case insensitive. If that is the case true is returned, and the operands are re-written appropriately.

This is a helper function for Expression classes that compares strings.

See also: ComparisonPlatform::useCaseInsensitiveComparator()

Definition at line 110 of file qvaluecomparison.cpp.

Referenced by QPatternist::ComparesCaseAware::compress(), compress(), QPatternist::GeneralComparison::compress(), and operatorID().

 {
     Q_ASSERT(op1);
     Q_ASSERT(op2);
 
     const ID iD = op1->id();
 
     if((iD == IDLowerCaseFN || iD == IDUpperCaseFN) && iD == op2->id())
     {
         /* Both are either fn:lower-case() or fn:upper-case(). */
 
         /* Replace the calls to the functions with its operands. */
         op1 = op1->operands().first();
         op2 = op2->operands().first();
 
         return true;
     }
     else
         return false;
 }

◆ operatorID()

AtomicComparator::Operator QPatternist::ValueComparison::operatorID ( ) const

inline

Returns: the operator that this ValueComparison is using.

Definition at line 113 of file qvaluecomparison_p.h.

Referenced by QPatternist::ComparisonIdentifier::matches().

         {
             return m_operator;
         }

◆ optimizationPasses()

OptimizationPass::List ValueComparison::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 131 of file qvaluecomparison.cpp.

 {
     return OptimizationPasses::comparisonPasses;
 }

◆ staticType()

SequenceType::Ptr ValueComparison::staticType ( ) const

virtual

Returns: always CommonSequenceTypes::ExactlyOneBoolean

Implements QPatternist::Expression.

Definition at line 144 of file qvaluecomparison.cpp.

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

◆ typeCheck()

Expression::Ptr ValueComparison::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 75 of file qvaluecomparison.cpp.

 {
     const Expression::Ptr me(PairContainer::typeCheck(context, reqType));
     const ItemType::Ptr t1(m_operand1->staticType()->itemType());
     const ItemType::Ptr t2(m_operand2->staticType()->itemType());
     Q_ASSERT(t1);
     Q_ASSERT(t2);
 
     if(*CommonSequenceTypes::Empty == *t1 ||
        *CommonSequenceTypes::Empty == *t2)
     {
         return EmptySequence::create(this, context);
     }
     else
     {
         prepareComparison(fetchComparator(t1, t2, context));
 
         return me;
     }
 }

Properties

◆ m_operator

const AtomicComparator::Operator QPatternist::ValueComparison::m_operator

private

Definition at line 130 of file qvaluecomparison_p.h.

Referenced by operatorID().

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

/src/xmlpatterns/expr/qvaluecomparison_p.h
/src/xmlpatterns/expr/qvaluecomparison.cpp

Public Functions

Static Public Functions

Properties

Additional Inherited Members

Detailed Description

Constructors and Destructors

◆ ValueComparison()

Functions

◆ accept()

◆ compress()

◆ evaluateSingleton()

◆ expectedOperandTypes()

◆ id()

◆ isCaseInsensitiveCompare()

◆ operatorID()

◆ optimizationPasses()

◆ staticType()

◆ typeCheck()

Properties

◆ m_operator