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    41 

    42 //

    43 //  W A R N I N G

    44 //  -------------

    45 //

    46 // This file is not part of the Qt API.  It exists purely as an

    47 // implementation detail.  This header file may change from version to

    48 // version without notice, or even be removed.

    49 //

    50 // We mean it.

    51 

    52 /**

    53  * @file

    54  * @short Contains Doxygen documentation for groups.

    55  */

    56 

    57 namespace QPatternist

    58 {

    59     /**

    60      * @short The abstract syntax tree nodes that implements the builtin

    61      * functions, such as @c fn:concat().

    62      *

    63      * @defgroup Patternist_functions Function Implementations

    64      * @author Frans Englich <frans.englich@nokia.com>

    65      */

    66 

    67     /**

    68      * @short The abstract syntax tree nodes that is generated for XPath,

    69      * XQuery, and XSL-T code.

    70      *

    71      * XPath's approach of compilation is traditional. An Abstract Syntax

    72      * Tree(AST) is built, where the Expression class is the abstract base

    73      * class for all kinds of implementations of expressions.

    74      *

    75      * What perhaps can be said to be characteristic for Patternist is that the

    76      * base class, Expression, performs a lot of work, and that sub-classes

    77      * declares what specific behaviors they need, which the Expression's

    78      * functions then bring into action.

    79      *

    80      * XPath expressions often have different amount of operands. For example,

    81      * the 'and' expression takes two, the context item(".") none, and the

    82      * if-expression three. To help expression implementations with that, there

    83      * exist the abstract EmptyContainer, SingleContainer, PairContainer,

    84      * TripleContainer, and UnlimitedContainer classes for avoiding duplicating

    85      * code.

    86      *

    87      * @defgroup Patternist_expressions Expressions

    88      * @author Frans Englich <frans.englich@nokia.com>

    89      */

    90 

    91     /**

    92      * @short Various classes that contains small utility functions.

    93      *

    94      * @defgroup Patternist Utility Classes

    95      * @author Frans Englich <frans.englich@nokia.com>

    96      */

    97 

    98     /**

    99      * @short Classes for the type system in the XQuery & XSL-T language.

   100      *

   101      * @defgroup Patternist_types Type system

   102      * @author Frans Englich <frans.englich@nokia.com>

   103      */

   104 

   105     /**

   106      * @defgroup Patternist_xdm XQuery/XPath Data Model

   107      * @author Frans Englich <frans.englich@nokia.com>

   108      */

   109 

   110     /**

   111      * @short Patternist's family of iterators in one of the most central parts

   112      * of Patternist's API, and are responsible for carrying, and typically

   113      * also creating, data.

   114      *

   115      * An iterator, which always is an Iterator sub-class, is similar to a

   116      * Java-style iterator. What signifies Patternist's iterators is that they

   117      * almost always contains business logic(which is the cause to their

   118      * efficiency).

   119      *

   120      * An example which illustrates this principle is the RangeIterator. When

   121      * the RangeExpression is told to create a sequence of integers between 1

   122      * and 1000, it doesn't enter a loop that allocates 1000 Integer instances,

   123      * but instead return an RangeIterator that incrementally creates the

   124      * numbers when asked to do so via its RangeIterator::next() function. If

   125      * it turns out that the expression that has the range expression as

   126      * operand only needs three items from it, that is what gets created, not

   127      * 1000.

   128      *

   129      * All iterators operates by that principle, perhaps suitably labeled as

   130      * "pull-based", "lazy loaded" or "serialized". Central for the XPath

   131      * language is that it filters and selects data, and the iterators supports

   132      * this well by letting the demand of the filter expressions(the callees)

   133      * decide how "much" source that gets computed. In this way the evaluation

   134      * of an expression tree can lead to a chain of pipelined iterators, where

   135      * the first asks the second for data and then performs its specific

   136      * operations, the second subsequently asks the third, and so forth.

   137      *

   138      * However, the iterators are not limited to be used for representing

   139      * sequences of items in the XPath Data Model. The Iterator is

   140      * parameterized on one argument, meaning any type of "units" can be

   141      * iterated, be it Item or any other. One use of this is in the

   142      * ExpressionSequence(which implements the comma operator) where it creates

   143      * Iterator instances over Expression instances -- its operands. The

   144      * parameterization is often used in combination with the MappingIterator

   145      * and the MappingCallback.

   146      *

   147      * @defgroup Patternist_iterators Iterators

   148      * @author Frans Englich <frans.englich@nokia.com>

   149      */

   150 }