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| ** This file is part of the QtXmlPatterns module of the Qt Toolkit. |
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| |
| #include "qcommonsequencetypes_p.h" |
| #include "qgenericsequencetype_p.h" |
| |
| #include "qfirstitempredicate_p.h" |
| |
| QT_BEGIN_NAMESPACE |
| |
| using namespace QPatternist; |
| |
| FirstItemPredicate::FirstItemPredicate(const Expression::Ptr &source) : SingleContainer(source) |
| { |
| } |
| |
| Item FirstItemPredicate::evaluateSingleton(const DynamicContext::Ptr &context) const |
| { |
| /* If our operand allows the empty sequence, this function can return Item(), otherwise |
| * it returns the first item. As simple as that. */ |
| return m_operand->evaluateSequence(context)->next(); |
| } |
| |
| SequenceType::Ptr FirstItemPredicate::staticType() const |
| { |
| const SequenceType::Ptr t(m_operand->staticType()); |
| return makeGenericSequenceType(t->itemType(), t->cardinality().toWithoutMany()); |
| } |
| |
| Expression::Ptr FirstItemPredicate::compress(const StaticContext::Ptr &context) |
| { |
| const Expression::Ptr me(SingleContainer::compress(context)); |
| if(me != this) |
| return me; |
| |
| if(m_operand->is(IDFirstItemPredicate)) |
| m_operand = m_operand->operands().first(); |
| |
| return me; |
| } |
| |
| SequenceType::List FirstItemPredicate::expectedOperandTypes() const |
| { |
| SequenceType::List result; |
| result.append(CommonSequenceTypes::ZeroOrMoreItems); |
| return result; |
| } |
| |
| ExpressionVisitorResult::Ptr FirstItemPredicate::accept(const ExpressionVisitor::Ptr &visitor) const |
| { |
| return visitor->visit(this); |
| } |
| |
| Expression::ID FirstItemPredicate::id() const |
| { |
| return IDFirstItemPredicate; |
| } |
| |
| QT_END_NAMESPACE |