| .. Algorithms/Querying Algorithms//count |40 |
| |
| count |
| ===== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename T |
| > |
| struct count |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns the number of elements in a ``Sequence`` that are identical to ``T``. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/count.hpp> |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+---------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===========================+===================================+ |
| | ``Sequence`` | |Forward Sequence| | A sequence to be examined. | |
| +---------------+---------------------------+-----------------------------------+ |
| | ``T`` | Any type | A type to search for. | |
| +---------------+---------------------------+-----------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| |
| For any |Forward Sequence| ``s`` and arbitrary type ``t``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef count<s,t>::type n; |
| |
| :Return type: |
| |Integral Constant|. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef count_if< s,is_same<_,T> >::type n; |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Exactly ``size<s>::value`` comparisons for identity. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector<int,char,long,short,char,short,double,long> types; |
| typedef count<types, short>::type n; |
| |
| BOOST_MPL_ASSERT_RELATION( n::value, ==, 2 ); |
| |
| |
| See also |
| -------- |
| |
| |Querying Algorithms|, |count_if|, |find|, |find_if|, |contains|, |lower_bound| |
| |
| |
| .. 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) |
