Re: [Boost-users] Needs advices on design ( mpl or processor )

My problem is not to calculate the actually size, but move the calculation from the instantiation into the definition of the library. On Fri, Jan 6, 2012 at 11:04 PM, Nevin Liber wrote:

On 6 January 2012 13:26, Larry Evans wrote:

...

So, IIUC, you want (as the name compressed_enums suggests) want to sum the sizes of each enum,

Assuming size is the number of unique values in a given enum, you want to sum the ceiling of log2 of the size of each enum to determine how many bits you need. http://www.boost.org/doc/libs/1_48_0/libs/integer/doc/html/boost_integer/log... can help with this (although it computes floor(log2(n))).  Note: to get an even denser packing where different enums can share the same bit, remove "ceiling of" from the previous sentence.

Example:  if the first enum has 4 distinct values and the second enum has 8 distinct values, you need to be about to store 4x8=32 distinct combinations.  ceil(log2(4)) + ceil(log2(8)) == 2 + 3 == 5 bits. --  Nevin ":-)" Liber  mailto:nevin@eviloverlord.com  (847) 691-1404 _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users