| .. Metafunctions/Miscellaneous//sizeof_ |100 |
| |
| sizeof\_ |
| ======== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename X |
| > |
| struct sizeof\_ |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns the result of a ``sizeof(X)`` expression wrapped into an |
| |Integral Constant| of the corresponding type, ``std::size_t``. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/sizeof.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Metafunction| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-------------------+-------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===================+===========================================+ |
| | ``X`` | Any type | A type to compute the ``sizeof`` for. | |
| +---------------+-------------------+-------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For an arbitrary type ``x``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef sizeof_<x>::type n; |
| |
| |
| :Return type: |
| |Integral Constant|. |
| |
| :Precondition: |
| ``x`` is a complete type. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef size_t< sizeof(x) > n; |
| |
| |
| |
| Complexity |
| ---------- |
| |
| Constant time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| struct udt { char a[100]; }; |
| |
| BOOST_MPL_ASSERT_RELATION( sizeof_<char>::value, ==, sizeof(char) ); |
| BOOST_MPL_ASSERT_RELATION( sizeof_<int>::value, ==, sizeof(int) ); |
| BOOST_MPL_ASSERT_RELATION( sizeof_<double>::value, ==, sizeof(double) ); |
| BOOST_MPL_ASSERT_RELATION( sizeof_<udt>::value, ==, sizeof(my) ); |
| |
| |
| See also |
| -------- |
| |
| |Metafunctions|, |Integral Constant|, |size_t| |
| |
| |
| .. 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) |