Re: [boost] Re: A couple of issues in submitting typelists to boost

From: Chuck Allison (cda_at_[hidden])
Date: 2001-11-25 23:07:00

FWIW, I could write a hefty volume on what our faculty doesn't know about
C++.

----- Original Message -----
From: "Andrei Alexandrescu" <andrewalex_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Sunday, November 25, 2001 8:39 PM
Subject: Re: [boost] Re: A couple of issues in submitting typelists to boost

> From: "Beman Dawes" <bdawes_at_[hidden]>
> > At 07:32 AM 11/25/2001, John Maddock wrote:
> >  >Of course they all do the same thing, so we only need one of these -
it
> >  >depends on which way you look at it I guess - personally I prefer
> >  >"is_public_base", as it's the easiest to understand what it does (I
> > always
> >  >get "superclass" and "subclass" mixed up, and I'm sure I'm not alone!)
>
> But it's easy. As you draw the inheritance hierarchy, superclasses come
> above subclasses. That's how I remember it :o).
>
> By the way, being a student has its perks - you learn lots of interesting
> things. For example, I found out that Eiffel uses an inheritance scheme
> (called covariant) that's conceptually unsound (you can get type errors at
> runtime). This in spite of Eiffel's creator making a lot of arguments in
> favopr of the practical advantages of that scheme. Java gets one (called
> equivariant) that's correct (yet limited), except for arrays where it has
to
> carry out and check at runtime some type information. C++ implements an
> equivariant scheme as well, plus covariant return types which are a bonus
> because they are conceptually sound. Nobody in the class knew that C++
> implements covariant return types - including faculty...
>
> > Any number of otherwise intelligent people mix up "superclass" and
> > "subclass", which aren't really usual C++ terms anyhow.  OTOH,
> > is_public_base uses familiar C++ terminology.
>
> Yes, but is_public_base suffers of the "who's first and who's second"
> problem. Per public demand, I changed super_subclass to base_derived. So
> base_derived<T, U>::value is true is T is the base and U is the derived.
>
>
> Andrei
>
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