On 11 May 2014, at 09:36 pm, Larry Evans wrote

Hi Dominik,

On 05/08/14 12:30, Dominik Charousset wrote post http://article.gmane.org/gmane.comp.lib.boost.devel/250747 including: [snip]

...

[3] https://github.com/Neverlord/boost.actor/blob/a0cab41e2946df7d751c59dfead0c2...

However, I have a question about the implementation.

https://github.com/Neverlord/boost.actor/blob/a0cab41e2946df7d751c59dfead0c2...

uses a recursive call using a List<typename ...Ts> which is 1 shorter than the argument list, List<T0, Ts...>. Why not just pass sizeof...(T0, Ts...):

http://en.cppreference.com/w/cpp/language/sizeof...

and keep adding indices while decreasing this sizeof value, as done here:

http://svn.boost.org/svn/boost/sandbox/variadic_templates/boost/mpl/package_...

in the package_range_c template class where:

Start value would be 0 and Finish value would be sizeof...(T0, Ts...)

It achieves the same result, but without producing unneeded instantiations. For example:

package_range_c<std::size_t,0,sizeof...(mpl::vector<T0,T2,T3>>::type package_range_c<std::size_t,0,sizeof...(mpl::vector<S0,S2,S3>>::type

would produce 1 instantiation of:

package_range_c<std::size_t,0,3>

whereas the int_list.hpp code would, IIUC, produce the same number of instantiations for the T's and S's.

Wouldn't using the sizeof... method be easier to understand as well as produce few instantions?

Reviewing the code again, I think there's really no good reason to recurse over Ts. Doing the unrolling in il_indices recursively with only two specializations is a simple design, but the instantiations of type_list are indeed unnecessary. Also, the dependency to type_list could be dropped when unrolling based on sizeof....

-regards, Larry

NOTE: I tried to post to the newsgroup; however, apparently my post got lost :(

Let's hope the list is working again...