forked from boostorg/core
83 lines
2.5 KiB
Plaintext
83 lines
2.5 KiB
Plaintext
[/
|
|
/ Copyright (c) 2001, 2002, 2006 Peter Dimov
|
|
/ Copyright (c) 2002 David Abrahams
|
|
/ Copyright (c) 2002 Aleksey Gurtovoy
|
|
/ Copyright (c) 2003, 2004 Douglas Gregor
|
|
/ Copyright (c) 2009 Ronald Garcia
|
|
/ Copyright (c) 2014 Glen Joseph Fernandes
|
|
/
|
|
/ 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:ref ref]
|
|
|
|
[simplesect Authors]
|
|
|
|
* Jaakko J\u00E4rvi
|
|
* Peter Dimov
|
|
* Douglas Gregor
|
|
* Dave Abrahams
|
|
* Frank Mori Hess
|
|
* Ronald Garcia
|
|
|
|
[endsimplesect]
|
|
|
|
[section Introduction]
|
|
|
|
The Ref library is a small library that is useful for passing
|
|
references to function templates (algorithms) that would
|
|
usually take copies of their arguments. It defines the class
|
|
template `boost::reference_wrapper<T>`, two functions
|
|
`boost::ref` and `boost::cref` that return instances of
|
|
`boost::reference_wrapper<T>`, a function `boost::unwrap_ref`
|
|
that unwraps a `boost::reference_wrapper<T>` or returns a
|
|
reference to any other type of object, and the two traits
|
|
classes `boost::is_reference_wrapper<T>` and
|
|
`boost::unwrap_reference<T>`.
|
|
|
|
The purpose of `boost::reference_wrapper<T>` is to contain a
|
|
reference to an object of type `T`. It is primarily used to
|
|
"feed" references to function templates (algorithms) that take
|
|
their parameter by value.
|
|
|
|
To support this usage, `boost::reference_wrapper<T>` provides
|
|
an implicit conversion to `T&`. This usually allows the
|
|
function templates to work on references unmodified.
|
|
|
|
`boost::reference_wrapper<T>` is both CopyConstructible and
|
|
Assignable (ordinary references are not Assignable).
|
|
|
|
The `expression boost::ref(x)` returns a
|
|
`boost::reference_wrapper<X>(x)` where `X` is the type of `x`.
|
|
Similarly, `boost::cref(x)` returns a
|
|
`boost::reference_wrapper<X const>(x)`.
|
|
|
|
The expression `boost::unwrap_ref(x)` returns a
|
|
`boost::unwrap_reference<X>::type&` where `X` is the type of
|
|
`x`.
|
|
|
|
The expression `boost::is_reference_wrapper<T>::value` is
|
|
`true` if `T` is a `reference_wrapper`, and `false` otherwise.
|
|
|
|
The type-expression `boost::unwrap_reference<T>::type` is
|
|
`T::type` if `T` is a `reference_wrapper`, `T` otherwise.
|
|
|
|
[endsect]
|
|
|
|
[xinclude ref_reference.xml]
|
|
|
|
[section Acknowledgments]
|
|
|
|
`ref` and `cref` were originally part of the Tuple library by
|
|
Jaakko J\u00E4rvi. They were "promoted to `boost::` status" by
|
|
Peter Dimov because they are generally useful. Douglas Gregor
|
|
and Dave Abrahams contributed `is_reference_wrapper` and
|
|
`unwrap_reference`. Frank Mori Hess and Ronald Garcia
|
|
contributed `boost::unwrap_ref`.
|
|
|
|
[endsect]
|
|
|
|
[endsect]
|