| [/ |
| / Copyright (c) 2001, 2002 Peter Dimov and Multi Media Ltd. |
| / Copyright (c) 2003-2008 Peter Dimov |
| / |
| / 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:limitations Limitations] |
| |
| As a general rule, the function objects generated by `bind` take their |
| arguments by reference and cannot, therefore, accept non-const temporaries or |
| literal constants. This is an inherent limitation of the C++ language in its |
| current (2003) incarnation, known as the [@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1385.htm forwarding problem]. |
| (It will be fixed in the next standard, usually called C++0x.) |
| |
| The library uses signatures of the form |
| |
| template<class T> void f(T & t); |
| |
| to accept arguments of arbitrary types and pass them on unmodified. As noted, |
| this does not work with non-const r-values. |
| |
| On compilers that support partial ordering of function templates, a possible |
| solution is to add an overload: |
| |
| template<class T> void f(T & t); |
| template<class T> void f(T const & t); |
| |
| Unfortunately, this requires providing 512 overloads for nine arguments, which |
| is impractical. The library chooses a small subset: for up to two arguments, |
| it provides the const overloads in full, for arities of three and more it |
| provides a single additional overload with all of the arguments taken by const |
| reference. This covers a reasonable portion of the use cases. |
| |
| [endsect] |
