AMDG Hicham Mouline wrote:

I just realized you can instantiate fusion vector objects (forgot fusion is about runtime too)

So I have this example:

struct A { explicit A(int) {} };

struct B { explicit B(int) {} };

struct C { explicit C(int) {} };

class Derived1 { public: Derived1 () : members( A(5), B(5), C(5) ) {} private: const boost::fusion::vector< A, B, C > members; };

All members are constructed with the same argument(s) : 5

Now: 1. I may have 20 members in vector.... Is there a way not to explicitly construct them in the Derived1 ctor

You need to create a fusion sequence that consists of the same arguments repeated many times. template<class T> struct constant { constant(const T& v) : value(v) {} T value; typedef T result_type; template<class U> T operator()(const U&) const { return(value); } }; ... members(boost::fusion::transform_view(boost::mpl::range_c<0, 20>(), constant<int>(5)))

2. Derived3 and Derived7 have the same vector of members. Is there a way, inside Derived3 and 7, to take the vector from Derived1?

fusion containers can be copied from each other. The copy will be done member wise. In Christ, Steven Watanabe