| .. Metafunctions/Miscellaneous//inherit_linearly |40 |
| |
| inherit_linearly |
| ================ |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Types |
| , typename Node |
| , typename Root = empty_base |
| > |
| struct inherit_linearly |
| : fold<Types,Root,Node> |
| { |
| }; |
| |
| |
| Description |
| ----------- |
| |
| A convenience wrapper for ``fold`` to use in the context of sequence-driven |
| class composition. Returns the result the successive application of binary |
| ``Node`` to the result of the previous ``Node`` invocation (``Root`` if it's |
| the first call) and every type in the |Forward Sequence| ``Types`` in order. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/inherit_linearly.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Metafunction| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===============================+===================================================+ |
| | ``Types`` | |Forward Sequence| | Types to inherit from. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | ``Node`` | Binary |Lambda Expression| | A derivation metafunction. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | ``Root`` | A class type | A type to be placed at the root of the class | |
| | | | hierarchy. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Forward Sequence| ``types``, binary |Lambda Expression| ``node``, and arbitrary |
| class type ``root``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef inherit_linearly<types,node,root>::type r; |
| |
| :Return type: |
| A class type. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef fold<types,root,node>::type r; |
| |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Exactly ``size<types>::value`` applications of ``node``. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| template< typename T > struct tuple_field |
| { |
| T field; |
| }; |
| |
| template< typename T > |
| inline |
| T& field(tuple_field<T>& t) |
| { |
| return t.field; |
| } |
| |
| typedef inherit_linearly< |
| vector<int,char const*,bool> |
| , inherit< _1, tuple_field<_2> > |
| >::type tuple; |
| |
| |
| int main() |
| { |
| tuple t; |
| |
| field<int>(t) = -1; |
| field<char const*>(t) = "text"; |
| field<bool>(t) = false; |
| |
| std::cout |
| << field<int>(t) << '\n' |
| << field<char const*>(t) << '\n' |
| << field<bool>(t) << '\n' |
| ; |
| } |
| |
| |
| See also |
| -------- |
| |
| |Metafunctions|, |Algorithms|, |inherit|, |empty_base|, |fold|, |reverse_fold| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| 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) |
