Larry Evans wrote:
On 07/08/10 02:11, Timothy Madden wrote:
Larry Evans wrote: [snip]
Maybe you could just use pointers to the enclosing composite, like in:
#include <tr1/tuple> #include <vector>
struct tuple_tree : std::tr1::tuple < float , int , std::vector<tuple_tree*>
{ };
I can use vector<tuple_tree> directly, with no pointer needed, and it works,
Hmm... I'm surprised. I would have thought a pointer would be needed to break the recursion because, otherwise, the tuple_tree CTOR would create an infinite tree. But now that I think more about it, the pointer is within the std::vector. No infinite tree is created because the vector is initially empty.
Well, as you can see, some people say you were correct, after all, because C++ might place a requirement to always use complete types for containers.
but I would expect boost::make_recursive_variant<> to do the substitution correctly so I could create the type in-place.
This structure is part of a bigger tuple of containers in my code, and using tuple_tree would require me to declare it in advance, separately, while make_recursive_variant would create the needed type in-place.
Here is my code:
[...]
std::vector < boost::tuple < std::basic_string<TCHAR>, // uuid int, // revision std::basic_string<TCHAR>, // name std::basic_string<TCHAR>, // desc std::basic_string<TCHAR>, // status std::basic_string<TCHAR>, // statusName, std::basic_string<TCHAR>, // memo std::basic_string<TCHAR>, // designFileName std::vector < UIOVarEntry
What happens if you just use this, IOW, just std::vector<UIOVarEntry>. There'd be no infinite tree created for the reasons cited earlier. Wouldn't this satisfy your requirements? [...]
It bothers me that to compose my large structure I need some previously declared class UIOVarEntry, to hold a certain number of components from my big typedef. With make_recursive_variant I could have all my structure declared in-place at once. Thank you, Timothy Madden