Re: [boost] Re: concept archetypes

From: Douglas Gregor (gregod_at_[hidden])
Date: 2002-10-15 16:47:06

On Tuesday 15 October 2002 04:38 pm, Craig Henderson wrote:
> "v m" <boost_vam_at_[hidden]> wrote in message
> > 3. There are several differences between the standard
> > and the current archetype classes, especially the
> > iterator archetype classes. For example, almost all
> > the relational operators (operator==, operator!= etc)
> > have a return type of bool whereas the standard
> > requires a return type convertible to bool. Would
> > changing the return type have any unwanted
> > consequences (not particularly in the
> > concept_archetype.hpp) ?
>
> How is this not conforming to the standard? The return type is bool. The
> standard requires a return type that is convertible to bool (Table 72).
> bool is implicitly convertible to bool. What's the problem?
> The synopsis of the iterator class in 24.2 itself defines the return type
> as bool.

It's conforming, but it's not the best possible archetype. Concept archetypes 
should push the requirements as far as possible. So the relational operators 
for the archetype should each return a unique type that is implicitly 
convertible to 'bool' (thus making sure that no code assumes that the return 
type is exactly 'bool').

        Doug