Re: Ada 200X

["Robert I. Eachus" <rieachus@attbi.com>]

Vinzent Hoefler wrote:

> Mmh, well. I encounter a third variant quite often. For instance let's
> take a short look at a part of the good old TurboVision object
> hierarchy:
> 
>                         +-------+
>                         �TObject�
>                         +-------+
>                             |
>                          +-----+
>                          �TView�
>                          +-----+
>                             |
>       +----------------------------------------------+
>       |       |        |       |      |      |       |
>  +----------+ |  +----------+  | +--------+  |   +------+
>  |TScrollBar| |  |TInputLine|  | |TCluster|  |   |TGroup|
>  +----------+ |  +----------+  | +--------+  |   +------+
>               |                |     |       |       |
>         +-----------+     +--------+ | +-----------+ +-------------+
>         �TStaticText�     �THistory� | �TListViewer�               |
>         +-----------+     +--------+ | +-----------+               |
>               |                      |       |                     |
>         +-----------+                |    +-----------+            |
>         |           |                |    |           |            |
>      +------+  +----------+          | +--------+ +--------------+ |
>      |TLabel|  |TParamText|          | |TListBox| |THistoryViewer| |
>      +------+  +----------+          | +--------+ +--------------+ |
>                               +------+--------+           +--------+
>                               |      |        |           |
>                               | +-----------+ |       +-------+
>                               | |TCheckBoxes| |       |TWindow|
>                               | +-----------+ |       +-------+
>                         +-------------+ +----------------+ |
>                         |TRadioButtons| |TMultiCheckBoxes| |
>                         +-------------+ +----------------+ |
>                                                    +-------------+
>                                                    |             |
>                                            +--------------+  +-------+
>                                            |THistoryWindow|  |TDialog|
>                                            +--------------+  +-------+

> This rather looks like a tree. And I doubt, any medium sized OO-System
> would be much different from that just because it's Ada.

First, lets get a view that doesn't hide the structure:

TObject
   TView
     TScrollBar
     TStaticText
       TLabel
       TParamText
     TInputLine
     THistory
     TCluster
       TRadioButtons
       TCheckBoxes
       TMultiCheckBoxes
     TListViewer
       TListBox
       THistoryViewer
     TGroup
       TWindow
         THistoryWindow
         TDialog

Let's actually put our Ada hats on and look at that hierarchy.  The 
TObject vs. TView looks to be methodological not logical. Notice that 
there is a descendent TListViewer, which is the only view related direct 
child.)  TView has seven children.  If you redid this in Ada, I don't 
know if TCluster and TGroup would remain as 'real' children but I am 
sure that TWindow would get elevated.  A typical Ada Model-View 
hierarchy would have Object and View as parents and most other types 
descended from one or the other.

Of course, if I were to reimplement this hierarchy in Ada, I'd try as 
hard as possible to keep the original structure.  I might or might not 
manage to swallow the naming convention though. ;-)