Abstract class for representing XQuery expressions. Expression are divided into ParseExpr and Value classes. @author BaseX Team, BSD License @author Christian Gruen
| 30 | * @author Christian Gruen |
| 31 | */ |
| 32 | public abstract class Expr extends ExprInfo { |
| 33 | /** |
| 34 | * Checks if the updating semantics are satisfied. |
| 35 | * This function is only called if any updating expression was found in the query. |
| 36 | * @throws QueryException query exception |
| 37 | */ |
| 38 | public abstract void checkUp() throws QueryException; |
| 39 | |
| 40 | /** |
| 41 | * Compiles and optimizes the expression, assigns types and cardinalities. |
| 42 | * @param cc compilation context |
| 43 | * @return optimized expression |
| 44 | * @throws QueryException query exception |
| 45 | */ |
| 46 | public abstract Expr compile(CompileContext cc) throws QueryException; |
| 47 | |
| 48 | /** |
| 49 | * Optimizes an already compiled expression without recompiling its sub-expressions. |
| 50 | * @param cc compilation context |
| 51 | * @return optimized expression |
| 52 | * @throws QueryException query exception |
| 53 | */ |
| 54 | @SuppressWarnings("unused") |
| 55 | public Expr optimize(final CompileContext cc) throws QueryException { |
| 56 | return this; |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Evaluates the expression and returns an iterator on the resulting items. |
| 61 | * If this method is not implemented, either {@link #value(QueryContext)} or |
| 62 | * {@link #item(QueryContext, InputInfo)} must be implemented instead. |
| 63 | * @param qc query context |
| 64 | * @return iterator |
| 65 | * @throws QueryException query exception |
| 66 | */ |
| 67 | public abstract Iter iter(QueryContext qc) throws QueryException; |
| 68 | |
| 69 | /** |
| 70 | * Evaluates the expression and returns the resulting value. |
| 71 | * If this method is not implemented, either {@link #iter(QueryContext)} or |
| 72 | * {@link #item(QueryContext, InputInfo)} must be implemented instead. |
| 73 | * @param qc query context |
| 74 | * @return value |
| 75 | * @throws QueryException query exception |
| 76 | */ |
| 77 | public abstract Value value(QueryContext qc) throws QueryException; |
| 78 | |
| 79 | /** |
| 80 | * Evaluates the expression and returns the resulting item, |
| 81 | * or {@link Empty#VALUE} if the expression yields an empty sequence. |
| 82 | * If this method is not implemented, either {@link #iter(QueryContext)} or |
| 83 | * {@link #value(QueryContext)} must be implemented instead. |
| 84 | * @param qc query context |
| 85 | * @param ii input info (can be {@code null}; required for those {@link Value} instances |
| 86 | * that have no input info) |
| 87 | * @return item or {@link Empty#VALUE} |
| 88 | * @throws QueryException query exception |
| 89 | */ |
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