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- [/==============================================================================
- Copyright (C) 2001-2011 Joel de Guzman
- Copyright (C) 2001-2011 Hartmut Kaiser
- Distributed under the Boost Software License, Version 1.0. (See accompanying
- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- ===============================================================================/]
- [section:auto Auto Parser]
- [heading Description]
- This module includes the description of the `auto_` parser. This parser
- can be used to automatically create a parser based on the supplied attribute
- type.
- [heading Header]
- // forwards to <boost/spirit/home/qi/auto.hpp>
- #include <boost/spirit/include/qi_auto.hpp>
- Also, see __include_structure__.
- [heading Namespace]
- [table
- [[Name]]
- [[`boost::spirit::auto_ // alias: boost::spirit::qi::auto_`]]
- ]
- [heading Model of]
- [:__primitive_parser_concept__]
- [heading Expression Semantics]
- Semantics of an expression is defined only where it differs from, or is
- not defined in __primitive_generator_concept__.
- [table
- [[Expression] [Description]]
- [[`auto_`] [Create a parser instance compatible with the
- supplied attribute type and use it for input
- matching.]]
- ]
- [heading Additional Requirements]
- The `auto_` parsers can be used to match input for any data type for which
- a mapping to a parser type is defined (the meta function
- `traits::create_parser_exists` returns `mpl::true_`).
- The following table outlines the predefined mapping rules from the attribute
- type to the parser type. These rules are applied recursively to create the parser
- type which can be used to match input for the given attribute type.
- [table
- [[Attribute type] [Parser type]]
- [[`char`, `wchar_t`] [`standard::char_`, `standard_wide::char_`]]
- [[`short`, `int`, `long`] [`short_`, `int_`, `long_`]]
- [[`unsigned short`, `unsigned int`, `unsigned long`]
- [`ushort_`, `uint_`, `ulong_`]]
- [[`float`, `double`, `long double`] [`float_`, `double_`, `long_double`]]
- [[`long long`, `unsigned long long`]
- [`long_long`, `ulong_long`]]
- [[`bool`] [`bool_`]]
- [[Any (STL) container] [Kleene Star (unary `'*'`)]]
- [[Any Fusion sequence] [Sequence operator (`'>>'`)]]
- [[`boost::optional<>`] [Optional operator (unary `'-'`)]]
- [[`boost::variant<>`] [Alternative operator (`'|'`)]]
- ]
- It is possible to add support for any custom data type by implementing a
- specialization of the customization point __customize_create_parser__. This
- customization can be used also to redefined any of the predefined mappings.
- [heading Attributes]
- [table
- [[Expression] [Attribute]]
- [[`auto_`] [`hold_any`]]
- ]
- [important The attribute type `hold_any` exposed by the `auto_`
- parser is semantically and syntactically equivalent to
- the type implemented by __boost_any__. It has been added to /Spirit/
- as it has better a performance and a smaller footprint if compared to
- __boost_any__.
- ]
- [heading Complexity]
- [:The complexity of the `auto_` parser depends on the supplied attribute type. Each
- attribute type results in a different parser type to be instantiated which
- defines the overall complexity.]
- [heading Example]
- [note The test harness for the example(s) below is presented in the
- __qi_basics_examples__ section.]
- Some includes:
- [reference_includes]
- Some using declarations:
- [reference_qi_using_declarations_auto]
- And a class definition used in the examples:
- [reference_qi_complex]
- [reference_qi_auto_complex]
- Some usage examples of `auto_` parsers:
- [reference_qi_auto]
- [endsect]
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