Re: A bad counterintuitive behaviour of Ada about OO

[Shark8 <OneWingedShark@gmail.com>]

On 07-Aug-14 07:34, J-P. Rosen wrote:
> Classification makes sense only if you have
> heterogeneous data structures that manipulate various types belonging to
> a same class.

I'd note that the heterogeneous data-structure needn't be strict; 
consider if you will an instruction set for a [virtual] CPU -- different 
instructions could have different numbers of parameters and therefore 
not be [strictly] heterogeneous. (Granted that all of these instructions 
would have another, if implicit, common parameter: the CPU.)

So, you could end up with abstract types:
   Instruction         -- Base/common interface.
   Arity_0_Instruction -- Common structure of 0 param instructions.
   Arity_1_Instruction -- Common structure of 1 param instructions.
   Arity_2_Instruction -- Common structure of 2 param instructions.
   Arity_3_Instruction -- Common structure of 3 param instructions.
and having all the instructions derive from the proper Arity.

Granted, you could also do the above [structurally] using a 
variant-record with multiple nestings.