BOOST_PP_REPEAT with array

boost, boost-preprocessor, c++

Solution

You could do it like this:

#define TYPES (type_A)(type_B)(type_X)


#define GENERATE_TUPLE(maR, maNamespace, maIndex, maType) \
  BOOST_PP_COMMA_IF(maIndex) boost::optional<maNamespace :: maType>


#define GENERATE_GETTER(maR, maNamespace, maIndex, maType) \
  boost::optional<maNamespace :: maType> const& maType () const { return boost::get<maIndex>(data); }


struct E1
{
  typedef boost::tuple<
    BOOST_PP_SEQ_FOR_EACH_I(GENERATE_TUPLE, N, TYPES)
  > data_type;

  BOOST_PP_SEQ_FOR_EACH_I(GENERATE_GETTER, N, TYPES)

  data_type data;
};

The `N` argument corresponds to the `maNamespace` parameter. You can of course use this argument in any other way (it's just passed through verbatim), such as hardcoding `N` into the macros (and passing a dummy in the argument), or encoding even the identifier `data` in there, etc.

Problem

I have struct like : ``` struct E1 { typedef boost::tuple< boost::optional< N::type_A >, // N - namespace boost::optional< N::type_B >, ................... boost::optional< N::type_X > //arbitrary number of, maximal is 7 > data_type; // for access by name boost::optional<N::type_A> const& type_A() const { return boost::get<0>(data); } boost::optional<N::type_B> const& type_B() const { return boost::get<1>(data); } ..................................... boost::optional<N::type_X> const& type_X() const { return boost::get<2>(data); } data_type data; }; ``` Q: how I may create this structure using BOOST preprocessors? For me known only type_A, type_B, ..., type_X name of types. It's need me, because I must create a lot of structures like that, only changing type_A, type_B, ... types. In common case, can I use boost preprocessor array or set?

Original source