Re: [boost] [geometry] view_as concept casting

Subject: Re: [boost] [geometry] view_as concept casting
From: Gordon Woodhull (gordon_at_[hidden])
Date: 2009-01-10 00:15:06

On Jan 9, 2009, at 4:21 PM, David Abrahams wrote:
> on Fri Jan 09 2009, "Simonson, Lucanus J" <lucanus.j.simonson-AT- 
> intel.com> wrote:
>> I implemented the above hierarchy as
>> struct pwh{};
>> struct p : pwh{};
>> struct p45wh : pwh{};
>> struct p45 : virtual p, p45wh {};
>> struct p90wh : p45wh;
>> struct p90 : virtual p45, p90wh {};
>> But wasn't keen on a virtual pointer in a tag, so took out virtual  
>> keyword.
>
> Yeah, you shouldn't need it.

Interestingly, virtual inheritance of tags shouldn't have any runtime  
cost.  There's an interesting example in the Templates Complete Guide  
which uses virtual inheritance for a default policy scheme.

For the same reason (never instantiated) not necessary here.