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| 2 | // (C) Copyright Edward Diener 2011-2015 |
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| 3 | // Use, modification and distribution are subject to the Boost Software License, |
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| 4 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
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| 5 | // http://www.boost.org/LICENSE_1_0.txt). |
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| 6 | |
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| 7 | #if !defined(BOOST_VMD_IS_EMPTY_HPP) |
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| 8 | #define BOOST_VMD_IS_EMPTY_HPP |
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| 9 | |
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| 10 | #include <boost/vmd/detail/setup.hpp> |
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| 11 | |
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| 12 | #if BOOST_PP_VARIADICS |
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| 13 | |
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| 14 | #include <boost/preprocessor/punctuation/is_begin_parens.hpp> |
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| 15 | #include <boost/vmd/detail/is_empty.hpp> |
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| 16 | |
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| 17 | /* |
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| 18 | |
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| 19 | The succeeding comments in this file are in doxygen format. |
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| 20 | |
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| 21 | */ |
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| 22 | |
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| 23 | /** \file |
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| 24 | */ |
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| 25 | |
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| 26 | /** \def BOOST_VMD_IS_EMPTY(...) |
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| 27 | |
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| 28 | \brief Tests whether its input is empty or not. |
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| 29 | |
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| 30 | The macro checks to see if the input is empty or not. |
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| 31 | It returns 1 if the input is empty, else returns 0. |
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| 32 | |
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| 33 | The macro is a variadic macro taking any input. |
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| 34 | For the VC++8 compiler (VS2005) the macro takes a single parameter of input to check. |
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| 35 | |
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| 36 | The macro is not perfect, and can not be so. The problem |
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| 37 | area is if the input to be checked is a function-like |
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| 38 | macro name, in which case either a compiler error can result |
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| 39 | or a false result can occur. |
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| 40 | |
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| 41 | This macro is a replacement, using variadic macro support, |
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| 42 | for the undocumented macro BOOST_PP_IS_EMPTY in the Boost |
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| 43 | PP library. The code is taken from a posting by Paul Mensonides |
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| 44 | of a variadic version for BOOST_PP_IS_EMPTY, and changed |
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| 45 | in order to also support VC++. |
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| 46 | |
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| 47 | .... = variadic input, for VC++8 this must be a single parameter |
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| 48 | |
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| 49 | returns = 1 if the input is empty, 0 if it is not |
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| 50 | |
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| 51 | It is recommended to append BOOST_PP_EMPTY() to whatever input |
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| 52 | is being tested in order to avoid possible warning messages |
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| 53 | from some compilers about no parameters being passed to the macro |
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| 54 | when the input is truly empty. |
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| 55 | |
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| 56 | */ |
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| 57 | |
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| 58 | #if BOOST_VMD_MSVC_V8 |
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| 59 | |
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| 60 | #define BOOST_VMD_IS_EMPTY(sequence) \ |
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| 61 | BOOST_VMD_DETAIL_IS_EMPTY_IIF \ |
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| 62 | ( \ |
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| 63 | BOOST_PP_IS_BEGIN_PARENS \ |
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| 64 | ( \ |
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| 65 | sequence \ |
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| 66 | ) \ |
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| 67 | ) \ |
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| 68 | ( \ |
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| 69 | BOOST_VMD_DETAIL_IS_EMPTY_GEN_ZERO, \ |
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| 70 | BOOST_VMD_DETAIL_IS_EMPTY_PROCESS \ |
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| 71 | ) \ |
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| 72 | (sequence) \ |
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| 73 | /**/ |
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| 74 | |
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| 75 | #else |
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| 76 | |
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| 77 | #define BOOST_VMD_IS_EMPTY(...) \ |
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| 78 | BOOST_VMD_DETAIL_IS_EMPTY_IIF \ |
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| 79 | ( \ |
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| 80 | BOOST_PP_IS_BEGIN_PARENS \ |
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| 81 | ( \ |
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| 82 | __VA_ARGS__ \ |
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| 83 | ) \ |
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| 84 | ) \ |
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| 85 | ( \ |
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| 86 | BOOST_VMD_DETAIL_IS_EMPTY_GEN_ZERO, \ |
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| 87 | BOOST_VMD_DETAIL_IS_EMPTY_PROCESS \ |
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| 88 | ) \ |
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| 89 | (__VA_ARGS__) \ |
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| 90 | /**/ |
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| 91 | |
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| 92 | #endif /* BOOST_VMD_MSVC_V8 */ |
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| 93 | |
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| 94 | #endif /* BOOST_PP_VARIADICS */ |
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| 95 | #endif /* BOOST_VMD_IS_EMPTY_HPP */ |
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| 96 | |
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