Implements XPath 2.0's castable as expression. More...

#include <qcastableas_p.h>

Inheritance diagram for QPatternist::CastableAs:

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

	CastableAs (const Expression::Ptr &operand, const SequenceType::Ptr &targetType)

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

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

virtual SequenceType::List	expectedOperandTypes () const

virtual SequenceType::Ptr	staticType () const

ItemType::Ptr	targetType () const

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

Public Functions inherited from QPatternist::SingleContainer
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 Item	evaluateSingleton (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 ()

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 ()

Properties
const SequenceType::Ptr	m_targetType

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::SingleContainer
	SingleContainer (const Expression::Ptr &operand)

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::CastingPlatform< CastableAs, false >
Item	cast (const Item &sourceValue, const ReportContext::Ptr &context) const

	CastingPlatform (const ReportContext::ErrorCode code=ReportContext::FORG0001)

void	checkTargetType (const ReportContext::Ptr &context) const

bool	prepareCasting (const ReportContext::Ptr &context, const ItemType::Ptr &sourceType)

Protected Variables inherited from QPatternist::SingleContainer
Expression::Ptr	m_operand

Detailed Description

Implements XPath 2.0's castable as expression.

See also: XML Path Language (XPath) 2.0, 3.10.3 Castable

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

Definition at line 73 of file qcastableas_p.h.

Constructors and Destructors

◆ CastableAs()

CastableAs::CastableAs	(	const Expression::Ptr &	operand,
		const SequenceType::Ptr &	targetType
	)

Definition at line 56 of file qcastableas.cpp.

                                                      : SingleContainer(operand),
                                                          m_targetType(tType)
 {
     Q_ASSERT(tType);
     Q_ASSERT(!tType->cardinality().allowsMany());
     Q_ASSERT(tType->itemType()->isAtomicType());
 }

Functions

◆ accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 152 of file qcastableas.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

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

virtual

Overridden to const fold to true when the target type is a type which casting to always succeeds. This is the type identical to the target type, xs:string, and xs:untypedAtomic.

Reimplemented from QPatternist::Expression.

Definition at line 86 of file qcastableas.cpp.

 {
     const Expression::Ptr me(SingleContainer::compress(context));
 
     if(me != this) /* We already managed to const fold, how convenient. */
         return me;
 
     const AtomicType::Ptr t(m_targetType->itemType());
 
     const SequenceType::Ptr opType(m_operand->staticType());
 
     /* Casting to these always succeeds, assuming the cardinality also matches,
      * although the cardinality can fail. */
     if((   *t == *BuiltinTypes::xsString
         || *t == *BuiltinTypes::xsUntypedAtomic
         || *t == *opType->itemType())
        &&(m_targetType->cardinality().isMatch(opType->cardinality())))
     {
         return wrapLiteral(CommonValues::BooleanTrue, context, this);
     }
     else
         return me;
 }

◆ evaluateEBV()

bool CastableAs::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 65 of file qcastableas.cpp.

 {
     Item item;
 
     if(m_operand->staticType()->cardinality().allowsMany())
     {
         const Item::Iterator::Ptr it(m_operand->evaluateSequence(context));
         item = it->next();
 
         if(it->next())
             return false;
     }
     else
         item = m_operand->evaluateSingleton(context);
 
     if(item)
         return !cast(item, context).as<AtomicValue>()->hasError();
     else
         return m_targetType->cardinality().allowsEmpty();
 }

◆ expectedOperandTypes()

SequenceType::List CastableAs::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 140 of file qcastableas.cpp.

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

◆ staticType()

SequenceType::Ptr CastableAs::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 147 of file qcastableas.cpp.

 {
     return CommonSequenceTypes::ExactlyOneBoolean;
 }

◆ targetType()

ItemType::Ptr QPatternist::CastableAs::targetType ( ) const

inline

Definition at line 97 of file qcastableas_p.h.

         {
             return m_targetType->itemType();
         }

◆ typeCheck()

Expression::Ptr CastableAs::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 110 of file qcastableas.cpp.

 {
     checkTargetType(context);
     const Expression::Ptr me(SingleContainer::typeCheck(context, reqType));
 
     return me;
     if(BuiltinTypes::xsQName->xdtTypeMatches(m_targetType->itemType()))
     {
         const SequenceType::Ptr seqt(m_operand->staticType());
         /* We can cast a string literal, an xs:QName value, and an
          * empty sequence(if empty is allowed), to xs:QName. */
         if(m_operand->is(IDStringValue) ||
            BuiltinTypes::xsQName->xdtTypeMatches(seqt->itemType()) ||
            (*seqt->itemType() == *CommonSequenceTypes::Empty && m_targetType->cardinality().allowsEmpty()))
         {
             return wrapLiteral(CommonValues::BooleanTrue, context, this)->typeCheck(context, reqType);
         }
         else
             return wrapLiteral(CommonValues::BooleanFalse, context, this)->typeCheck(context, reqType);
     }
     else
     {
         /* Let the CastingPlatform look up its AtomicCaster. */
         prepareCasting(context, m_operand->staticType()->itemType());
 
         return me;
     }
 }

Properties

◆ m_targetType

const SequenceType::Ptr QPatternist::CastableAs::m_targetType

private

Definition at line 103 of file qcastableas_p.h.

Referenced by compress(), evaluateEBV(), targetType(), and typeCheck().

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

/src/xmlpatterns/expr/qcastableas_p.h
/src/xmlpatterns/expr/qcastableas.cpp

Public Functions

Properties

Additional Inherited Members

Detailed Description

Constructors and Destructors

◆ CastableAs()

Functions

◆ accept()

◆ compress()

◆ evaluateEBV()

◆ expectedOperandTypes()

◆ staticType()

◆ targetType()

◆ typeCheck()

Properties

◆ m_targetType