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| 2 | // Copyright (C) 2009-2012 Lorenzo Caminiti |
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| 3 | // Distributed under the Boost Software License, Version 1.0 |
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| 4 | // (see accompanying file LICENSE_1_0.txt or a copy at |
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| 5 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 6 | // Home at http://www.boost.org/libs/utility/identity_type |
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| 7 | |
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| 8 | /** @file |
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| 9 | Wrap type expressions with round parenthesis so they can be passed to macros |
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| 10 | even if they contain commas. |
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| 11 | */ |
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| 12 | |
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| 13 | #ifndef BOOST_IDENTITY_TYPE_HPP_ |
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| 14 | #define BOOST_IDENTITY_TYPE_HPP_ |
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| 15 | |
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| 16 | #include <boost/type_traits/function_traits.hpp> |
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| 17 | |
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| 18 | /** |
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| 19 | @brief This macro allows to wrap the specified type expression within extra |
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| 20 | round parenthesis so the type can be passed as a single macro parameter even if |
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| 21 | it contains commas (not already wrapped within round parenthesis). |
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| 22 | |
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| 23 | @Params |
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| 24 | @Param{parenthesized_type, |
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| 25 | The type expression to be passed as macro parameter wrapped by a single set |
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| 26 | of round parenthesis <c>(...)</c>. |
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| 27 | This type expression can contain an arbitrary number of commas. |
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| 28 | } |
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| 29 | @EndParams |
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| 30 | |
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| 31 | This macro works on any C++03 compiler (it does not use variadic macros). |
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| 32 | |
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| 33 | This macro must be prefixed by <c>typename</c> when used within templates. |
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| 34 | Note that the compiler will not be able to automatically determine function |
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| 35 | template parameters when they are wrapped with this macro (these parameters |
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| 36 | need to be explicitly specified when calling the function template). |
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| 37 | |
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| 38 | On some compilers (like GCC), using this macro on abstract types requires to |
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| 39 | add and remove a reference to the specified type. |
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| 40 | */ |
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| 41 | #define BOOST_IDENTITY_TYPE(parenthesized_type) \ |
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| 42 | /* must NOT prefix this with `::` to work with parenthesized syntax */ \ |
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| 43 | boost::function_traits< void parenthesized_type >::arg1_type |
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| 44 | |
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| 45 | #endif // #include guard |
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| 46 | |
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| 47 | |
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