1[/============================================================================== 2 Copyright (C) 2001-2011 Joel de Guzman 3 Copyright (C) 2001-2011 Hartmut Kaiser 4 5 Distributed under the Boost Software License, Version 1.0. (See accompanying 6 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7===============================================================================/] 8 9[section:auto Auto Parser] 10 11[heading Description] 12 13This module includes the description of the `auto_` parser. This parser 14can be used to automatically create a parser based on the supplied attribute 15type. 16 17[heading Header] 18 19 // forwards to <boost/spirit/home/qi/auto.hpp> 20 #include <boost/spirit/include/qi_auto.hpp> 21 22Also, see __include_structure__. 23 24[heading Namespace] 25 26[table 27 [[Name]] 28 [[`boost::spirit::auto_ // alias: boost::spirit::qi::auto_`]] 29] 30 31[heading Model of] 32 33[:__primitive_parser_concept__] 34 35[heading Expression Semantics] 36 37Semantics of an expression is defined only where it differs from, or is 38not defined in __primitive_generator_concept__. 39 40[table 41 [[Expression] [Description]] 42 [[`auto_`] [Create a parser instance compatible with the 43 supplied attribute type and use it for input 44 matching.]] 45] 46 47[heading Additional Requirements] 48 49The `auto_` parsers can be used to match input for any data type for which 50a mapping to a parser type is defined (the meta function 51`traits::create_parser_exists` returns `mpl::true_`). 52The following table outlines the predefined mapping rules from the attribute 53type to the parser type. These rules are applied recursively to create the parser 54type which can be used to match input for the given attribute type. 55 56[table 57 [[Attribute type] [Parser type]] 58 [[`char`, `wchar_t`] [`standard::char_`, `standard_wide::char_`]] 59 [[`short`, `int`, `long`] [`short_`, `int_`, `long_`]] 60 [[`unsigned short`, `unsigned int`, `unsigned long`] 61 [`ushort_`, `uint_`, `ulong_`]] 62 [[`float`, `double`, `long double`] [`float_`, `double_`, `long_double`]] 63 [[`long long`, `unsigned long long`] 64 [`long_long`, `ulong_long`]] 65 [[`bool`] [`bool_`]] 66 [[Any (STL) container] [Kleene Star (unary `'*'`)]] 67 [[Any Fusion sequence] [Sequence operator (`'>>'`)]] 68 [[`boost::optional<>`] [Optional operator (unary `'-'`)]] 69 [[`boost::variant<>`] [Alternative operator (`'|'`)]] 70] 71 72It is possible to add support for any custom data type by implementing a 73specialization of the customization point __customize_create_parser__. This 74customization can be used also to redefined any of the predefined mappings. 75 76[heading Attributes] 77 78[table 79 [[Expression] [Attribute]] 80 [[`auto_`] [`hold_any`]] 81] 82 83[important The attribute type `hold_any` exposed by the `auto_` 84 parser is semantically and syntactically equivalent to 85 the type implemented by __boost_any__. It has been added to /Spirit/ 86 as it has better a performance and a smaller footprint if compared to 87 __boost_any__. 88] 89 90[heading Complexity] 91 92[:The complexity of the `auto_` parser depends on the supplied attribute type. Each 93 attribute type results in a different parser type to be instantiated which 94 defines the overall complexity.] 95 96[heading Example] 97 98[note The test harness for the example(s) below is presented in the 99 __qi_basics_examples__ section.] 100 101Some includes: 102 103[reference_includes] 104 105Some using declarations: 106 107[reference_qi_using_declarations_auto] 108 109And a class definition used in the examples: 110 111[reference_qi_complex] 112[reference_qi_auto_complex] 113 114Some usage examples of `auto_` parsers: 115 116[reference_qi_auto] 117 118[endsect] 119