| .. Sequences/Intrinsic Metafunctions//clear |
| |
| clear |
| ===== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| > |
| struct clear |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns an empty sequence |concept-identical| to ``Sequence``. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/clear.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Tag Dispatched Metafunction| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-----------------------------------+---------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===================================+=======================================+ |
| | ``Sequence`` | |Extensible Sequence| or | A sequence to get an empty "copy" of. | |
| | | |Extensible Associative Sequence| | | |
| +---------------+-----------------------------------+---------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Extensible Sequence| or |Extensible Associative Sequence| ``s``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef clear<s>::type t; |
| |
| :Return type: |
| |Extensible Sequence| or |Extensible Associative Sequence|. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef erase< s, begin<s>::type, end<s>::type >::type t; |
| |
| |
| :Postcondition: |
| ``empty<s>::value == true``. |
| |
| |
| Complexity |
| ---------- |
| |
| Amortized constant time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector_c<int,1,3,5,7,9,11> odds; |
| typedef clear<odds>::type nothing; |
| |
| BOOST_MPL_ASSERT(( empty<nothing> )); |
| |
| |
| See also |
| -------- |
| |
| |Extensible Sequence|, |Extensible Associative Sequence|, |erase|, |empty|, |begin|, |end| |
| |
| |
| .. 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) |