On 01/04/2005 11:52 AM, christopher diggins wrote:
I have written a union-style type similar to boost::variant which allows [snip] 2. the data size is huge = summation of the size of the individual types plus sizeof(bool) * #types.
Could you use the method for our_storage_size in: http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/indexed_types/composite_sum.hpp?rev=1.2&view=auto To calculate the maximum of the individual sizes and then just allocate storage for this max size? [snip]
union-list is that it uses and provides an index to access the type of its contents.
This, IMHO, is important. In the above indexed_types directory, there's typemap_unsigned.hpp which allows using unsigned indices instead of enumerations to access the elements. This was designed to allow the convenience of mpl's sequences; however, it also requires the possibly time consuming use of mpl's at_c and size. I don't know if it's really a significant time consumer, but it'd be nice if your method could somehow be adapted to avoid this. I've tried to think of a way to use mpl's inherit_linearly; however, I think it can't be done because, in order to use indexed accesss, all the type arguments of the inherited classes have to be identical except for the index. Maybe someone else can think of a workaround?