Re: How to test object hierarchy

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

Robert I. Eachus wrote:

> Dmytry Lavrov wrote:
> 
>>>I think that IF Ada should have multiple dispatch on different types...
> 
> In Ada, if and where you need it, you can get multiple dispatching.
> There are of course many different patterns that correspond to multiple
> dispatching, and if you want the most general pattern:
> 
> function "+" (L, R: Object) return Object;
> 
> Where unlike normal Ada, L, R and the return value can be different
> specific types.  This can be done, but you actually have to do some
> extra work "under the covers."
> 
> Normally you would declare the visible "+" as:
> 
> function "+" (L: Object; R: Object'Class) return Object'Class;
> 
> Then in the private part you would have a function which is called by
> the visible "+" but dispatches on the second parameter, and result type:
> 
> function Add (L: Object'Class; R: Object) return Object;
> 
> Or L may be of some general representation type.  But from experience,
> doing all this is a lot of work, and you don't want to even think about
> extending Object beyond the initial set of specific types.  You don't
> have to rethink the entire structure when you do that, but it may be the
> only way to produce something that is understandable to humans.

This is an argument in favor of implementing MD in Ada, I suppose (:-))

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de