QPatternist::RangeExpression Class Reference

Implements XPath 2.0's to expression. More...

#include <qrangeexpression_p.h>

Inheritance diagram for QPatternist::RangeExpression:

Public Functions
virtual ExpressionVisitorResult::Ptr	accept (const ExpressionVisitor::Ptr &visitor) const
virtual Item::Iterator::Ptr	evaluateSequence (const DynamicContext::Ptr &) const
virtual Item	evaluateSingleton (const DynamicContext::Ptr &) const
virtual SequenceType::List	expectedOperandTypes () const
virtual Expression::Properties	properties () const
	RangeExpression (const Expression::Ptr &operand1, const Expression::Ptr &operand2)
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)
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 bool	evaluateEBV (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
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 ()

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::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 XPath 2.0's to expression.

Despite its name, RangeExpression is not related to RangeVariableDeclaration.

See also

XML Path Language (XPath) 2.0, 3.3.1 Constructing Sequences

RangeIterator

Author

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

Definition at line 75 of file qrangeexpression_p.h.

Constructors and Destructors

RangeExpression()

RangeExpression::RangeExpression	(	const Expression::Ptr &	operand1,
		const Expression::Ptr &	operand2
	)

Definition at line 56 of file qrangeexpression.cpp.

                                                                : PairContainer(operand1, operand2)
{
}

Functions

accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 165 of file qrangeexpression.cpp.

{
    return visitor->visit(this);
}

evaluateSequence()

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

virtual

Evaluate this Expression by iterating over it. This is a central function for evaluating expressions.

Expressions must always always return a valid QAbstractXmlForwardIterator and may never return 0. If an empty result is of interest to be returned, the EmptyIterator should be returned.

The default implementation returns a SingletonIterator over the item returned from evaluateSingleton().

Note

This function may raise an exception when calling, not only when QAbstractXmlForwardIterator::next() is called on the return value. This is because in some cases evaluateSingleton() is called directly.

Reimplemented from QPatternist::Expression.

Definition at line 61 of file qrangeexpression.cpp.

{
    const Item s(m_operand1->evaluateSingleton(context));

    if(!s)
        return CommonValues::emptyIterator;

    const Item e(m_operand2->evaluateSingleton(context));
    if(!e)
        return CommonValues::emptyIterator;

    const xsInteger start = s.as<Numeric>()->toInteger();
    const xsInteger end = e.as<Numeric>()->toInteger();

    if(start > end)
        return CommonValues::emptyIterator;
    else if(start == end)
        return makeSingletonIterator(s);
    else
        return Item::Iterator::Ptr(new RangeIterator(start, RangeIterator::Forward, end));
}

evaluateSingleton()

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

virtual

It's likely that this function gets called if staticType() inferred the cardinality to an exact number. In that case, we know that the first arguments is the same as the second argument.

Reimplemented from QPatternist::Expression.

Definition at line 83 of file qrangeexpression.cpp.

{
    return m_operand1->evaluateSingleton(context);
}

expectedOperandTypes()

SequenceType::List RangeExpression::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 88 of file qrangeexpression.cpp.

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

properties()

Expression::Properties RangeExpression::properties ( ) const

virtual

Disables compression for optimization reasons. For example, the expression "1 to 1000" would consume thousand allocated instances of Integer, and RangeIterator is well suited for dynamic evaluation.

Returns

Expression::DisableElimination

Reimplemented from QPatternist::Expression.

Definition at line 160 of file qrangeexpression.cpp.

{
    return Expression::DisableElimination;
}

staticType()

SequenceType::Ptr RangeExpression::staticType ( ) const

virtual

Returns

always CommonSequenceTypes::ZeroOrMoreIntegers

Implements QPatternist::Expression.

Definition at line 96 of file qrangeexpression.cpp.

{
    /* This logic makes the Cardinality more specific. */
    Cardinality::Count from;
    bool hasFrom;

    if(m_operand1->is(IDIntegerValue))
    {
        from = m_operand1->as<Literal>()->item().as<Integer>()->toInteger();
        hasFrom = true;
    }
    else
    {
        hasFrom = false;
        from = 0;
    }

    /* We can't check whether to is -1 since maybe the user wrote -1. Hence
     * hasTo is required. */
    bool hasTo;
    Cardinality::Count to;

    if(m_operand2->is(IDIntegerValue))
    {
        const xsInteger asInt = m_operand2->as<Literal>()->item().as<Integer>()->toInteger();
        to = asInt;

        if(to == asInt)
            hasTo = true;
        else
        {
            /* Cardinality::Count is not the same as type xsInteger. We had overflow. */
            to = -1;
            hasTo = false;
        }
    }
    else
    {
        to = -1;
        hasTo = false;
    }

    if(hasTo && hasFrom)
    {
        if(from > to)
        {
            /* The query is incorrectly written, we'll evaluate to the empty sequence.
             * Just return what's correct. */
            return CommonSequenceTypes::ZeroOrMoreIntegers;
        }
        else
        {
            Cardinality::Count count = (to - from) + 1; /* + 1, since it's inclusive. */
            return makeGenericSequenceType(BuiltinTypes::xsInteger, Cardinality::fromExact(count));
        }
    }
    else
    {
        /* We can't do fromExact(from, -1) since the latter can evaluate to a value that actually is
         * lower than from, although that unfortunately is very unlikely. */
        return CommonSequenceTypes::ZeroOrMoreIntegers;
    }
}

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

• /src/xmlpatterns/expr/qrangeexpression_p.h
• /src/xmlpatterns/expr/qrangeexpression.cpp