| .. Sequences/Intrinsic Metafunctions//order |
| |
| order |
| ===== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename Key |
| > |
| struct order |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns a unique unsigned |Integral Constant| associated with the key ``Key`` in |
| ``Sequence``. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/order.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Tag Dispatched Metafunction| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+---------------------------+-----------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===========================+===============================================+ |
| | ``Sequence`` | |Associative Sequence| | A sequence to query. | |
| +---------------+---------------------------+-----------------------------------------------+ |
| | ``Key`` | Any type | The queried key. | |
| +---------------+---------------------------+-----------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Associative Sequence| ``s``, and arbitrary type ``key``: |
| |
| .. parsed-literal:: |
| |
| typedef order<s,key>::type n; |
| |
| :Return type: |
| Unsigned |Integral Constant|. |
| |
| :Semantics: |
| If ``has_key<s,key>::value == true``, ``n`` is a unique unsigned |
| |Integral Constant| associated with ``key`` in ``s``; otherwise, |
| ``n`` is identical to ``void_``. |
| |
| |
| Complexity |
| ---------- |
| |
| Amortized constant time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef map< pair<int,unsigned>, pair<char,long> > m; |
| |
| BOOST_MPL_ASSERT_NOT(( is_same< order<m,int>::type, void\_ > )); |
| BOOST_MPL_ASSERT(( is_same< order<m,long>::type,void\_ > )); |
| |
| |
| |
| See also |
| -------- |
| |
| |Associative Sequence|, |has_key|, |count|, |map| |
| |
| |
| .. 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) |
