Re: [boost] fusion concepts

Subject: Re: [boost] fusion concepts
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2011-06-13 17:52:32

On Mon, Jun 13, 2011 at 2:41 PM, Robert Ramey <ramey_at_[hidden]> wrote:

> I'm trying to implement concept checking for at least parts of the
> boost::fusion library.  My motivations are several:
>
> a) I'm interested in making another library/program based on fusion and I
> believe that having implemented concepts will make this job easier.
>
> b) I'm interested in the concept checking concept and this is way to
> pracitice.
>
> Attached is the current state of my efforts.  I have a few problems with
> this. I think most of these are specific to fusion but maybe not.
>
[...]

> b)
> lines 34-38 illustrate a different problem.  I can't figure out what
> distance(i,j) is supposed to return. I would think that
> result_of::distance(i, j) should be a signed integer of some sort.  So I'm
> not understanding why this assertion traps.  I not sure if it's a side
> effect of the problem cited in a) above.
>

Just quickly addressing this and only this, without looking at the
referenced lines:  I would think distance(i,j) would be a Boost.MPL integral
constant.

- Jeff