QPatternist::EBVExtractor Class Reference

Calculates the Effective Boolean Value of its operand. More...

#include <qebvextractor_p.h>

Inheritance diagram for QPatternist::EBVExtractor:

Public Functions
virtual ExpressionVisitorResult::Ptr	accept (const ExpressionVisitor::Ptr &visitor) const
virtual const SourceLocationReflection *	actualReflection () const
	Returns this. More...
	EBVExtractor (const Expression::Ptr &operand)
virtual bool	evaluateEBV (const DynamicContext::Ptr &context) const
virtual SequenceType::List	expectedOperandTypes () const
virtual SequenceType::Ptr	staticType () const
	Returns always xs:boolean. More...
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 void	announceFocusType (const ItemType::Ptr &itemType)
virtual Expression::Ptr	compress (const StaticContext::Ptr &context)
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 ()

Static Public Functions
template<typename TSubClass , typename ThisType >
static Expression::Ptr	typeCheck (const StaticContext::Ptr &context, const SequenceType::Ptr &reqType, ThisType *const caller)
Static Public Functions inherited from QPatternist::Expression
static void	rewrite (Expression::Ptr &old, const Expression::Ptr &New, const StaticContext::Ptr &context)

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

Detailed Description

Calculates the Effective Boolean Value of its operand.

EBVExtractor performs functionality wise the same as fn:boolean(), but does it without the dependencies which FunctionCall requires.

There is code-duplication going on with BooleanFN.

See also

BooleanFN

Author

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

Definition at line 75 of file qebvextractor_p.h.

Constructors and Destructors

EBVExtractor()

EBVExtractor::EBVExtractor

(

const Expression::Ptr &

operand

)

Definition at line 53 of file qebvextractor.cpp.

                                                       : SingleContainer(operand)
{
}

Functions

accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 85 of file qebvextractor.cpp.

{
    return visitor->visit(this);
}

actualReflection()

const SourceLocationReflection * EBVExtractor::actualReflection ( ) const

virtual

Returns this.

Reimplemented from QPatternist::Expression.

Definition at line 80 of file qebvextractor.cpp.

{
    return m_operand->actualReflection();
}

evaluateEBV()

bool EBVExtractor::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 57 of file qebvextractor.cpp.

{
    return m_operand->evaluateEBV(context);
}

expectedOperandTypes()

SequenceType::List EBVExtractor::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 73 of file qebvextractor.cpp.

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

staticType()

SequenceType::Ptr EBVExtractor::staticType ( ) const

virtual

Returns always xs:boolean.

Implements QPatternist::Expression.

Definition at line 68 of file qebvextractor.cpp.

{
    return makeGenericSequenceType(BuiltinTypes::xsBoolean, Cardinality::exactlyOne());
}

typeCheck() [1/2]

Expression::Ptr EBVExtractor::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 62 of file qebvextractor.cpp.

{
    return typeCheck<SingleContainer>(context, reqType, this);
}

typeCheck() [2/2]

template<typename TSubClass , typename ThisType >

static Expression::Ptr QPatternist::EBVExtractor::typeCheck ( const StaticContext::Ptr &  context, const SequenceType::Ptr &  reqType, ThisType *const  caller  )

inlinestatic

Definition at line 92 of file qebvextractor_p.h.

        {
            if(*CommonSequenceTypes::EBV->itemType() == *reqType->itemType())
                return caller->operands().first()->typeCheck(context, reqType);
            else
                return caller->TSubClass::typeCheck(context, reqType);
        }

---

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

• /src/xmlpatterns/janitors/qebvextractor_p.h
• /src/xmlpatterns/janitors/qebvextractor.cpp