Re: Capabilities interact nicely with Substructural Types and Reactivity

On Thu, Sep 12, 2013 at 2:09 PM, Rob Meijer <rmeijer-qWit8jRvyhVmR6Xm/[email protected]> wrote:

> On Thu, September 12, 2013 18:21, David Barbour wrote:
> > I wasn't speaking of creating any *particular class*, but rather the
> > *ambient authority to `new` in general*.
> >  [..]
> > Private constructors have no effect on this at all.
> >
>
> On itself it might not, but when combined with other language features, it
> could:
>

>
> http://minorfs.wordpress.com/2013/01/18/raiicap-pattern-injected-singleton-alternative-for-c/


What I described (ambient authority to create state and identity, i.e.
*any* new objects)
and what everyone else here seems to be hearing (ambient authority to
create *specific* new objects) are very different issues. Unfortunately,
like many writers, I'm in a bad position to understand why this distinction
isn't as super-obvious and clear to everyone else as it is to me.

Could you explain how you think singletons are related?


>
> This pattern uses private-constructors, friends and templates and
> optionally polymorphism to create what in an o-cap version of C++ might be
> considered constructor caps.
>
> It would be very interesting to explore if such a construct could be
> possible in an ocap language.
>

Sealer/unsealer pairs can model the full gamut of nominative types, ADTs,
classes, private constructors, etc.. Even better, they can do so in a *first
class* manner. Sealer/unsealer pairs offer more expressiveness than ghost
types. They're pretty useful.

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