ceph/src/boost/libs/local_function/include/boost/local_function/detail/preprocessor/keyword/facility/is.hpp

   1
   2 // Copyright (C) 2009-2012 Lorenzo Caminiti
   3 // Distributed under the Boost Software License, Version 1.0
   4 // (see accompanying file LICENSE_1_0.txt or a copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6 // Home at http://www.boost.org/libs/local_function
   7
   8 #ifndef BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_HPP_
   9 #define BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_HPP_
  10
  11 // Boost.Preprocessor author P. Mensodines confirmed on an Boost email thread
  12 // (subject ``check if a token is a keyword (was "BOOST_PP_IS_UNARY()")'')
  13 // that it is OK to used `PP_IS_UNARY()` to check if tokens match predefined
  14 // "keyword" as it is done by the macros below (even if `PP_IS_UNARY()` is
  15 // technically only part of Boost.Preprocessor private API).
  16 #include <boost/preprocessor/detail/is_unary.hpp>
  17 #include <boost/preprocessor/cat.hpp>
  18 #include <boost/preprocessor/control/iif.hpp>
  19 #include <boost/preprocessor/tuple/eat.hpp>
  20
  21 // PRIVATE //
  22
  23 #define BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_(a, b) \
  24     BOOST_PP_IS_UNARY(BOOST_PP_CAT(a, b))
  25
  26 // PUBLIC //
  27
  28 // `checking_prefix ## tokens` expand to unary (e.g., `(1)`) iff `tokens` start
  29 // with keyword to check.
  30 #define BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_FRONT( \
  31         tokens, checking_prefix) \
  32     BOOST_PP_IIF(BOOST_PP_IS_UNARY(tokens), \
  33         /* on MSVC this check works even if tokens already unary but on */ \
  34         /* C++03 (including GCC) this check on non-unary tokens gives */ \
  35         /* a concatenation error -- so return false is tokens is not unary */ \
  36         0 BOOST_PP_TUPLE_EAT(2) \
  37     , \
  38         BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_ \
  39     )(checking_prefix, tokens)
  40
  41 // `token ## checking_postfix` expand to unary (e.g., `(1)`) iff `token` is the
  42 // keyword to check. This check only works if `token` is a single token, it
  43 // will always expand to 0 if token is multiple tokens (e.g., `const *this`).
  44 // This check will expand to 0 with no error if `token` starts with a
  45 // non-alphanumeric symbol (e.g., `*this`).
  46 #define BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_BACK( \
  47         token, checking_postfix) \
  48     BOOST_LOCAL_FUNCTION_DETAIL_PP_KEYWORD_FACILITY_IS_(token, checking_postfix)
  49
  50 #endif // #include guard
  51