Re: Type naming conventions: Any_Foo

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:qsee2v$par$1@gioia.aioe.org...
> On 2019-12-06 21:18, Jeffrey R. Carter wrote:
>> On 12/5/19 10:51 PM, Dmitry A. Kazakov wrote:
>>>
>>> Ada standard library uses _Type, e.g.
>>>
>>> generic
>>> type Element_Type (<>) is private;
>>> with function "=" (Left, Right : Element_Type) return Boolean is <>;
>>> package Ada.Containers.Indefinite_Holders
>>
>> Yes, and the ARM also includes such abominations as anonymous access 
>> types. Just because it's in the ARM doesn't mean it's the best way to do 
>> something. Element is be a better name for that formal type.
>
> No, it would be misleading. Element must be reserved for instances of the 
> type. They are actual elements. The type of an element is not an element, 
> these are two totally different things.

Agreed. Ada.Containers all have a function Element that retrieves a (copy 
of) a single element object from the container. If the type was named 
element, what would this function be called? Similarly, some of the 
parameters are called Element (thus, Element : Element_Type in many 
parameter lists); those also would need alternate names.

There were a number of ARG members that disliked the "_Type" notation, so we 
looked at alternatives. And we didn't find anything that worked as well. 
Sometimes, package design is about the "least bad" alternative.

                                     Randy.




>>> There are lots of cases in Ada, you certainly should know that. As a 
>>> practical example GtkAda declares all widget types twice:
>>>
>>> type Gtk_Button_Record is ...
>>> type Gtk_Button is access all Gtk_Button_Record'Class;
>>
>> No well designed library has public access types. You aren't required to 
>> use a library that does, and you aren't required to use access types.
>
> I am required to. There must be always be two types in a GUI, one 
> referential type and one implementation type. The widget implementation 
> object in GtkAda is Gtk_Button_Record. The widget referential object is 
> Gtk_Button. It could be a handle or a smart pointer type instead of plain 
> pointer, but there is no way to reduce it to a single type. So the problem 
> will persist.
>
> -- 
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de