Handling of sequence of non const reference

[Joel Falcou]

Currently, assigning or copying a fusion sequence of non const reference to another is not possible. Down into the code, the vectorN classes only has a vectorN( const Sequence& ) constructor that calls a const qualified from_sequence method from the base_type.

Sequence of reference has a nice use case of enabling strcuture of arrayArray of structure efficient application and this can't be doen with current Fusion.

Could all sequence be amended so passing a non const sequence as initialisation is dealt with correctly ?

[Joel de Guzman]

If you can provide a test case for a specific use case, I can look into this and implement a fusion wide mod. Thanks, Joel!

[Joel Falcou]

Test case for composite_reference, a class acting as a reference tuple onto an struct adapted as a fusion sequence

[Joel Falcou]

Error of former example

[Joel Falcou]

I Just attached a test case and the error I get. Adding:

  template <typename Sequence>
  static BOOST_PP_CAT(vector_data, N)
  init_from_sequence(Sequence& seq)
  {
      typedef typename result_of::begin<Sequence>::type I0;
      I0 i0 = fusion::begin(seq);
      BOOST_PP_REPEAT_FROM_TO(1, N, FUSION_ITER_DECL_VAR, _)
      return BOOST_PP_CAT(vector_data, N)(BOOST_PP_ENUM_PARAMS(N, *i));
  }

  template <typename Sequence>
  BOOST_PP_CAT(vector, N)(
      Sequence& seq
#if (N == 1)
    , typename boost::disable_if<is_convertible<Sequence, T0> >::type* /*dummy*/ = 0
#endif
      )
      : base_type(base_type::init_from_sequence(seq)) {}

to vector_n.hpp and re-preprocess fix the stuff. I guess other sequences may have similar mechanism. Not sure about any side effect tough.

[Joel de Guzman]

Fixed for vector. I'll leave this open as a reminder to fix other containers.