Small ordered set

Small ordered set

[Victor Porton]

I need a "container" which describes an ordered set of two elements maximum 
(Sources, Targets).

All possible examples:

[]
[Sources]
[Targets]
[Sources, Targets]
[Targets, Sources]

What is the best way to implement it in Ada2012?

-- 
Victor Porton - http://portonvictor.org

Re: Small ordered set

[Robert Eachus]

On Saturday, October 28, 2017 at 12:37:37 PM UTC-4, Victor Porton wrote:
> I need a "container" which describes an ordered set of two elements maximum 
> (Sources, Targets).
> 
> All possible examples:
> 
> []
> [Sources]
> [Targets]
> [Sources, Targets]
> [Targets, Sources]
> 
> What is the best way to implement it in Ada2012?

I think you end up with an enumeration type, and a discriminated type:

type Foo is (None, Sources, Targets, Sources_and_Targets, 
             Targets_and_Sources);

type Bar(F: Foo := None) is record
   case F is..
end record;

Use names more appropriate to the purpose of the objects.  I suspect that Sources and Targets will correspond to heads of linked lists, but a long as they are of limited size no problem.