Re: [Boost-users] Recursive variant problem

8 Jul 2010

      Larry Evans wrote:
...
On 07/07/10 09:53, Timothy Madden wrote:
...
Hi
I use the following type in my application:
boost::make_recursive_variant
    <
    boost::tuple
        <
        std::basic_string<TCHAR>,            // id
        std::basic_string<TCHAR>,            // name
        std::basic_string<TCHAR>,            // desc
        std::basic_string<TCHAR>,            // type
        std::basic_string<TCHAR>,            // value
        std::vector<boost::recursive_variant_>        // childList
        >
    >::type
However when I instantiate it and I try to populate (resize) the 
vector (member indexed 5 in the tuple, childList) I get:
     'boost::recursive_variant_' : class has no constructors
from Visual Studio 2008 SP1.
It looks like the boost::recursive_variant_ type is not substituted 
with  the type of the enclosing variant by the make_recursive_variant 
meta-function. Am I missing something ? Is this is bug ?
[...]
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, 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:

class UIOVarEntry:
public
boost::tuple
   <
     std::basic_string<TCHAR>,         // id
     std::basic_string<TCHAR>,         // name
     std::basic_string<TCHAR>,         // desc
     std::basic_string<TCHAR>,         // type
     std::basic_string<TCHAR>,         // value
     std::vector<UIOVarEntry>          // childList
...
{
};

typedef
boost::tuple
   <
     int,             // serviceID
     int,             // projectID
     int,             // version
     std::basic_string<TCHAR>,    // htmlData,
     std::basic_string<TCHAR>,    // uioDesignData
     std::vector
       <
         boost::tuple
           <
             bool,             		// isGroup
             std::basic_string<TCHAR>,   // uuid
             int,              		// version
             std::basic_string<TCHAR>,   // parentID
             std::basic_string<TCHAR>,   // prevID
             std::basic_string<TCHAR>,   // name,
             std::basic_string<TCHAR>,   // desc
             std::basic_string<TCHAR>,   // filename
             std::vector
               <
                 boost::tuple
                   <
                     std::basic_string<TCHAR>,   // slotID,
                     int,              		// revision
                     std::basic_string<TCHAR>,   // uioID
                     std::basic_string<TCHAR>,   // layout
                     std::basic_string<TCHAR>,   // variables
                     std::basic_string<TCHAR>    // imgName
                   >
               >             	// slotList
           >
       >,            // planPageList
     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
             /*
                 boost::make_recursive_variant
                   <
                     boost::tuple
                       <
                         std::basic_string<TCHAR>,         // id
                         std::basic_string<TCHAR>,         // name
                         std::basic_string<TCHAR>,         // desc
                         std::basic_string<TCHAR>,         // type
                         std::basic_string<TCHAR>,         // value
                         std::vector<boost::recursive_variant_>    // 
childList
                       >,
                     int,
                     float
                   >::type
             */
               >,              // varList
             std::vector< std::basic_string<TCHAR> > // wireframeList
           >
       >         // uioList
...
ProjectData;

Thank you,
Timothy Madden