id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
10027,Allow template parameters with types rather than hardcode typename in BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE (and friends),Jonas Lippuner <jonas@…>,Joel de Guzman,"Right now, the macro `BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE` creates

{{{
template<typename A, typename B>
struct MyStruct { ... };
}}}

from 

{{{
BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE(
  (A)(B),
  MyStruct,
  (A, foo)
  (B, bar)
)
}}}

But I want to put the class `template<int DIM> class Vector` into a Boost Fusion Struct. So the struct should allow template parameters that are not typenames. I would like to be able to write the following:

{{{
BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE(
  (int DIM)(typename B),
  MyStruct,
  (Vector<DIM>, foo)
  (B, bar)
)

// the above becomes
// template<int DIM, typename B>
// struct MyStruct { ... };

MyStruct<3, double> struct;
}}}

This does not currently work. The following is a working (but cumbersome) workaround (using C++11):

{{{
BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE(
  (DIM)(B),
  MyStructImpl,
  (Vector<DIM::value>, foo)
  (B, bar)
)

template<int DIM>
using MyStruct = MyStructImpl<boost::mpl::int_<DIM>>;

MyStruct<3, double> struct;
}}}

Maybe for backwards compatibility my proposed version of `BOOST_FUSION_DEFINE_TPL_STRUCT_INLINE` where template parameters are declared as `(int DIM)(typename B)` should be named `BOOST_FUSION_DEFINE_FLEXIBLE_TPL_STRUCT_INLINE`.",Feature Requests,new,To Be Determined,fusion,Boost 1.55.0,Problem,,,