224 lines
9.0 KiB
Plaintext
224 lines
9.0 KiB
Plaintext
[/==============================================================================
|
|
Copyright (C) 2001-2011 Hartmut Kaiser
|
|
Copyright (C) 2001-2011 Joel de Guzman
|
|
|
|
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:stream Stream Generators]
|
|
|
|
This module includes the description of the different variants of the `stream`
|
|
generator. It can be used to utilize existing streaming operators
|
|
(`operator<<(std::ostream&, ...)`) for output generation.
|
|
|
|
[heading Header]
|
|
|
|
// forwards to <boost/spirit/home/karma/stream.hpp>
|
|
#include <boost/spirit/include/karma_stream.hpp>
|
|
|
|
Also, see __include_structure__.
|
|
|
|
[section:stream Stream Generators (`stream`, `wstream`, etc.)]
|
|
|
|
[heading Description]
|
|
|
|
The `stream_generator` is a primitive which allows to use pre-existing standard
|
|
streaming operators for output generation integrated with __karma__. It
|
|
provides a wrapper generator dispatching the value to output to the stream
|
|
operator of the corresponding type. Any value `a` to be formatted using the
|
|
`stream_generator` will result in invoking the standard streaming operator
|
|
for its type `A`, for instance:
|
|
|
|
std::ostream& operator<< (std::ostream&, A const&);
|
|
|
|
[heading Header]
|
|
|
|
// forwards to <boost/spirit/home/karma/stream.hpp>
|
|
#include <boost/spirit/include/karma_stream.hpp>
|
|
|
|
Also, see __include_structure__.
|
|
|
|
[heading Namespace]
|
|
|
|
[table
|
|
[[Name]]
|
|
[[`boost::spirit::stream // alias: boost::spirit::karma::stream`]]
|
|
[[`boost::spirit::wstream // alias: boost::spirit::karma::wstream`]]
|
|
]
|
|
|
|
[heading Synopsis]
|
|
|
|
template <typename Char>
|
|
struct stream_generator;
|
|
|
|
[heading Template parameters]
|
|
|
|
[table
|
|
[[Parameter] [Description] [Default]]
|
|
[[`Char`] [The character type to use to generate
|
|
the output. This type will be used while
|
|
assigning the generated characters to the
|
|
underlying output iterator.] [`char`]]
|
|
]
|
|
|
|
[heading Model of]
|
|
|
|
[:__primitive_generator_concept__]
|
|
|
|
[variablelist Notation
|
|
[[`s`] [A variable instance of any type with a defined matching
|
|
streaming `operator<<()` or a __karma_lazy_argument__ that
|
|
evaluates to any type with a defined matching streaming
|
|
`operator<<()`.]]
|
|
]
|
|
|
|
[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]]
|
|
[[`stream`] [Call the streaming `operator<<()` for the type
|
|
of the mandatory attribute. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `char`.]]
|
|
[[`stream(s)`] [Call the streaming `operator<<()` for the type
|
|
of the immediate value `s`. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `char`.]]
|
|
[[`wstream`] [Call the streaming `operator<<()` for the type
|
|
of the mandatory attribute. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `wchar_t`.]]
|
|
[[`wstream(s)`] [Call the streaming `operator<<()` for the type
|
|
of the immediate value `s`. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `wchar_t`.]]
|
|
]
|
|
|
|
All generators listed in the table above are predefined specializations of the
|
|
`stream_generator<Char>` basic stream generator type described below. It is
|
|
possible to directly use this type to create stream generators using an
|
|
arbitrary underlying character type.
|
|
|
|
[table
|
|
[[Expression] [Semantics]]
|
|
[
|
|
[``stream_generator<
|
|
Char
|
|
>()``] [Call the streaming `operator<<()` for the type
|
|
of the mandatory attribute. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `Char`]]
|
|
[
|
|
[``stream_generator<
|
|
Char
|
|
>()(s)``] [Call the streaming `operator<<()` for the type
|
|
of the immediate value `s`. The output emitted
|
|
by this operator will be the result of the
|
|
`stream` generator. This generator never fails
|
|
(unless the underlying output stream reports an
|
|
error). The character type of the I/O ostream
|
|
is assumed to be `Char`.]]
|
|
]
|
|
|
|
[heading Additional Requirements]
|
|
|
|
All of the stream generators listed above require the type of the value to
|
|
generate output for (either the immediate value or the associated attribute) to
|
|
implement a streaming operator conforming to the usual I/O streams conventions
|
|
(where `attribute_type` is the type of the value to generate output for):
|
|
|
|
template <typename Ostream>
|
|
Ostream& operator<< (Ostream& os, attribute_type const& attr)
|
|
{
|
|
// type specific output generation
|
|
return os;
|
|
}
|
|
|
|
This operator will be called by the stream generators to gather the output for
|
|
the attribute of type `attribute_type`. All data streamed into the given
|
|
`Ostream` will end up being generated by the corresponding stream generator
|
|
instance.
|
|
|
|
[note If the `stream` generator is invoked inside a [karma_format `format`]
|
|
(or [karma_format `format_delimited`]) stream manipulator the `Ostream`
|
|
passed to the `operator<<()` will have registered (imbued) the same
|
|
standard locale instance as the stream the [karma_format `format`] (or
|
|
[karma_format `format_delimited`]) manipulator has been used with.
|
|
This ensures all facets registered (imbued) with the original I/O
|
|
stream object are used during output generation.
|
|
]
|
|
|
|
[heading Attributes]
|
|
|
|
[table
|
|
[[Expression] [Attribute]]
|
|
[[`stream`] [`hold_any`, attribute is mandatory (otherwise compilation will fail)]]
|
|
[[`stream(s)`] [__unused__]]
|
|
[[`wstream`] [`whold_any`, attribute is mandatory (otherwise compilation will fail)]]
|
|
[[`wstream(s)`] [__unused__]]
|
|
[[`stream_generator<Char>()`] [`basic_hold_any<Char>`, attribute is mandatory (otherwise compilation will fail)]]
|
|
[[`stream_generator<Char>()(s)`] [__unused__]]
|
|
]
|
|
|
|
[important The attribute type `hold_any` exposed by some of the stream
|
|
generators 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__.
|
|
]
|
|
|
|
[note In addition to their usual attribute of type `Attrib` all listed generators
|
|
accept an instance of a `boost::optional<Attrib>` as well. If the
|
|
`boost::optional<>` is initialized (holds a value) the generators behave
|
|
as if their attribute was an instance of `Attrib` and emit the value stored
|
|
in the `boost::optional<>`. Otherwise the generators will fail.]
|
|
|
|
[heading Complexity]
|
|
|
|
[:O(N), where N is the number of characters emitted by the stream generator]
|
|
|
|
[heading Example]
|
|
|
|
[note The test harness for the example(s) below is presented in the
|
|
__karma_basics_examples__ section.]
|
|
|
|
Some includes:
|
|
|
|
[reference_karma_includes]
|
|
|
|
Some using declarations:
|
|
|
|
[reference_karma_using_declarations_stream]
|
|
|
|
And a class definition used in the examples:
|
|
|
|
[reference_karma_complex]
|
|
[reference_karma_stream_complex]
|
|
|
|
Basic usage of `stream` generators:
|
|
|
|
[reference_karma_stream]
|
|
|
|
[endsect]
|
|
|
|
[endsect]
|