ceph/src/boost/libs/tti/doc/tti_why.qbk

   1 [/
   2   (C) Copyright Edward Diener 2011
   3   Distributed under the Boost Software License, Version 1.0.
   4   (See accompanying file LICENSE_1_0.txt or copy at
   5   http://www.boost.org/LICENSE_1_0.txt).
   6 ]
   7
   8 [section:tti_reason Why the TTI Library ?]
   9
  10 In the Boost Type Traits library there is compile time functionality for
  11 querying information about a C++ type. This information is very useful
  12 during template metaprogramming and forms the basis, along with the
  13 constructs of the Boost MPL library, and some other compile time
  14 libraries, for much of the template metaprogramming in Boost.
  15
  16 One area which is mostly missing in the Type Traits library is the ability
  17 to determine what C++ inner elements are part of a type, where the inner
  18 element may be a nested type, function or data member, static function or
  19 static data member, or class template.
  20
  21 There has been some of this functionality in Boost, both in already existing
  22 libraries and in libraries on which others have worked but which were
  23 never submitted for acceptance into Boost. An example with an existing Boost
  24 library is Boost MPL, where there is functionality, in the form of macros and metafunctions,
  25 to determine whether an enclosing type has a particular nested type or nested
  26 class template. An example with a library which was never submitted to Boost
  27 is the Concept Traits Library from which much of the functionality of this
  28 library, related to type traits, was taken and expanded.
  29
  30 It may also be possible that some other Boost libraries, highly dependent
  31 on advanced template metaprogramming techniques, also have internal
  32 functionality to introspect a type's elements at compile time. But to the best
  33 of my knowledge this sort of functionality has never been incorporated in
  34 a single Boost library. This library is an attempt to do so, and to bring
  35 a recognizable set of interfaces to compile-time type introspection to Boost
  36 so that other metaprogramming libraries can use them for their own needs.
  37
  38 [endsect]