Qt 4.8
Public Functions | Static Public Functions | List of all members
QPatternist::EBVExtractor Class Reference

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

#include <qebvextractor_p.h>

Inheritance diagram for QPatternist::EBVExtractor:
QPatternist::SingleContainer QPatternist::Expression QSharedData QPatternist::CppCastingHelper< Expression > QPatternist::SourceLocationReflection

Public Functions

virtual ExpressionVisitorResult::Ptr accept (const ExpressionVisitor::Ptr &visitor) const
 
virtual const SourceLocationReflectionactualReflection () 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::Ptrrewrite (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 ExpressionConstPtr
 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::PtrList
 
typedef QFlags< PropertyProperties
 
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< ExpressionPtr
 A smart pointer wrapping mutable Expression instances. More...
 
typedef ::QAbstractXmlForwardIterator< Expression::PtrQAbstractXmlForwardIterator
 
typedef QVector< Expression::PtrVector
 
- 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.

53  : SingleContainer(operand)
54 {
55 }
SingleContainer(const Expression::Ptr &operand)

Functions

◆ accept()

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

Implements QPatternist::Expression.

Definition at line 85 of file qebvextractor.cpp.

86 {
87  return visitor->visit(this);
88 }

◆ actualReflection()

const SourceLocationReflection * EBVExtractor::actualReflection ( ) const
virtual

Returns this.

Reimplemented from QPatternist::Expression.

Definition at line 80 of file qebvextractor.cpp.

81 {
82  return m_operand->actualReflection();
83 }
virtual const SourceLocationReflection * actualReflection() const
Returns this.

◆ 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.

58 {
59  return m_operand->evaluateEBV(context);
60 }
virtual bool evaluateEBV(const DynamicContext::Ptr &context) const

◆ 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.

74 {
75  SequenceType::List result;
77  return result;
78 }
static const SequenceType::Ptr ZeroOrMoreItems
void append(const T &t)
Inserts value at the end of the list.
Definition: qlist.h:507
The QList class is a template class that provides lists.
Definition: qdatastream.h:62

◆ staticType()

SequenceType::Ptr EBVExtractor::staticType ( ) const
virtual

Returns always xs:boolean.

Implements QPatternist::Expression.

Definition at line 68 of file qebvextractor.cpp.

69 {
70  return makeGenericSequenceType(BuiltinTypes::xsBoolean, Cardinality::exactlyOne());
71 }
static Cardinality exactlyOne()
static const AtomicType::Ptr xsBoolean

◆ 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
contextsupplies 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.
reqTypethe 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.

64 {
65  return typeCheck<SingleContainer>(context, reqType, this);
66 }

◆ 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.

95  {
96  if(*CommonSequenceTypes::EBV->itemType() == *reqType->itemType())
97  return caller->operands().first()->typeCheck(context, reqType);
98  else
99  return caller->TSubClass::typeCheck(context, reqType);
100  }
static const SequenceType::Ptr EBV

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