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

On 01/06/12 12:56, Allan Nielsen wrote:

...

Wouldn't that variable have to be large enough to contain all the enums. At first glance this looks like:

fusion::vector:

The idea is that four enums which each only can contain four values, can together only represent 256 ( 4^4) values which can be stored in a char.

This off cause assume that their associated values are defined from 0 to 3.

It also works for numbers which are not powers of 2:

enum A{ a0 = 0, a1 = 1, a2 = 2, a3 = 3, a4 = 4 }; enum B{ b0 = 0, b1 = 1, b2 = 2, b3 = 3, b4 = 4 };

CompressedEnums< unsigned char, CompressedEnum, CompressedEnum > ENUMS;

sizeof(ENUMS) == sizeof(unsigned char);

I do not know boost::fusion very well, but I do not think this use full for this.

I think you're right. IIRC, fusion::vector stores all its values in member variables name m1, m2, ...,mn, where, in your case: A m1; B m2; So, IIUC, you want (as the name compressed_enums suggests) want to sum the sizes of each enum, then create a buffer with at least that number of bits, and then check that that buffer size is < sizeof(StorageType). I've thought some more about the problem and started coding something; however, it's not complete, but you may be able to complete it. As it is, it just prints 3, which is: size_enum<E1>::size+sizer_enum<E1>::size BTW, the attached code uses variadic templates; however, I'm guessing you could easily use non-variadic template compiler after some code changes. HTH. -regards, Larry