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Copyright © 1999, 2000 Jaakko Järvi
Copyright © 2001, 2002 Peter Dimov
Copyright © 2002 David Abrahams
Subject to 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.
Table of Contents
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>,
the two functions
boost::ref and
boost::cref that return
instances of boost::reference_wrapper<T>, 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::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.
Last revised: November 10, 2006 at 13:27:05 -0500 |