Re: [boost] [challenge!] find a common domain

Subject: Re: [boost] [challenge!] find a common domain
From: Eric Niebler (eric_at_[hidden])
Date: 2010-05-19 18:54:29

On 5/19/2010 3:29 PM, Daniel Wallin wrote:
> On Tue, May 18, 2010 at 11:02:56PM -0700, Eric Niebler wrote:
>> 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.
> 
> Here's mine. It's decltype based, but I guess it could be sizeof based
> in C++03.

Wow! SO much simpler than my solution. I'll need to study this in depth.
I also specialized domain<default_domain> to insert an extra level in
the inheritance tree like you did. That's a great simplification, but it
took me a week to see that. Kudos. BTW, you're creating a zero-sized
array in sized_type<0>. I just bumped all the integers by one and it
works fine on msvc-10.

This looks more efficient at compile-time, too. I'll be embarrassed to
post my solution. :-O But not yet. Anybody care to eliminate decltype so
I can use this in Proto? Anybody think they can instantiate fewer templates?

(I think everybody who posts a solution will get a mention in Proto's
docs and in the code. Fair's fair.)

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com