Re: [boost] GIL - Generic Image Library Review - Begins October 5

From: David Abrahams (dave_at_[hidden])
Date: 2006-10-07 10:03:55

"Andy Little" <andy_at_[hidden]> writes:

>>> http://permalink.gmane.org/gmane.comp.lib.boost.devel/144195
>>>
>>> para 5
>>
>> ? I don't see anything there that amounts to "specifically telling you
>> not to use Concept docs."
>
> Concepts arent an established convention. 

Yes they certainly are.  Maybe you mean in-language concept support is
not an established convention?

> Read Doug Gregors post. They havent been finalised.

I'm quite aware of that.

> I knew exactly what you meant in that and other discussions.

Apparently not.  If you're referring to this:

  FWIW, once we have concept support in the language we will be using
  pseudosignatures rather than valid expressions to express syntactic
  constraints, so we can expect that to change.  In the meantime,
  though, the things that can be expressed using established
  conventions should be so expressed.

what I meant was that, although there is a well-established convention
for documenting concepts, it's very likely that the conventions for
documenting concepts will change in the near future.  Then I go on to
reiterate my general (not specific) position that established
conventions should be used wherever applicable.

This is *not* specifically telling you not to use proposed concept
declaration syntax in documentation any more than it's specifically
telling you not to insert emoticons into your concept tables.

If you had specifically raised the topic of using the new proposed
concept language syntax to do documentation, I would have said the
following things about it, specifically (I did consider this issue, so
I know what I was thinking):

  1. It's an interesting idea

  2. You'd have to write some very careful introductory material that
     explains to people how to interpret it, or at least makes
     reference to a particular proposal paper.

  3. Don't forget to express semantic requirements, which don't have a
     place in concept description syntax (I think that has changed in
     more recent proposals)

  4. Especially if you're not all that familiar with how to document
     concepts, I think it would probably be a good idea to go with the
     existing conventions, and only do something more adventurous once
     you're very comfortable with the sorts of things that need to be
     expressed in a concept specification.  For one thing, there are
     lots more examples out there of the existing convention to work
     from.

  5. Anyone doing this instead of following the convention ought to
     be able to supply a good reason for doing it.

In other words, I wouldn't have rejected the idea out-of-hand, but I'd
have asked you to justify your choice and suggested that you might
want to hold off until you had more experience writing concepts.

> Also I can say with a large amount of certainty that if I had
> presented PQS for another review, and had used Concept
> documentation, then it would be pointed out by you or others that I
> had been specifically told not to do so.
>
> Now I shall sit back and watch the goalposts move as if by magic ...

Thought experiment #1: is there possible outcome here -- other than me
conceding that I "specifically told you" something I never said or
meant to say -- that would convince you the goalposts aren't being
moved?

Thought experiment #2: what does someone who makes such a remark hope
to accomplish by it, and what does it _actually_ accomplish?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com