On 19/05/10 07:02, Eric Niebler wrote: <snip>
Your job: implement the deduce_domain3 template that finds the common domain of 3 domains. You're allowed to use decltype, but you get bonus points for a solution that doesn't. Bonus also for instantiating fewest templates. The challenge is for the ternary case, but your solution should scale to N domains. If your solution is better than mine, I'll use it in Proto and credit you!
I attach my solution for completeness, though I think Daniel's is neater. I used a similar idea to him, but without the use of sizeof/decltype, and with the distance-to-not_a_domain implemented as a metafunction, rather than injected into the definition of domain. I think we use about the same number of instantiations, but Daniel's lends itself to unrolling much more than mine. I might argue that my implementation is a little easier to follow than his, but it would be a pretty feeble claim. (Bah, if only my NNTP client had been cooperating yesterday this would have looked a little more impressive :)) John Bytheway