Re: A function that cannot be called?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2018-10-18 22:21, G.B. wrote:
> On 18.10.18 17:33, Stefan.Lucks@uni-weimar.de wrote:
>> On Thu, 18 Oct 2018, G.B. wrote:
>>
>>> There is a type declaration, I rememberd, in Ada, that
>>> does not allow any object of the type to be declared.
>>
>> What, exactly, is the point of your question?
> 
> Philip Wadler asked, on occasion[*], whether there was any programming
> language other than Haskell that had a (concrete, usable in the normal
> way I guess) type like ("unihabited") Void in Data.Void.  (The point is
> getting my feet wet at the shores of correspondences of logic, typed 
> lambdas,

You should probably start expressing what you want using clearer terms. 
A type has a set of values and a set of operations. A type can be a 
member of several classes of types.

1. What values the type in question must have?
2. What operations it must have?
3. Of which classes it must be a member?

E.g. the type proposed by Niklas:

    type Zilch is range 1 .. 0;

has an empty set of values, non empty set of operations. It is a member 
of the non-tagged classes Zilch'Base, universal integer etc.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de