Re: The old "Object.Method" syntax debate

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

Rodrigo Garcia wrote:

> "David C. Hoos" <david.c.hoos.sr@ada95.com> wrote in message
> news:vcprq15q8m344e@corp.supernews.com...
>> I dod not mean to suggest that the availability of "IntelliSense"
> justified
>> the
>> new syntax.  The new syntax would eliminate some code redundancy, as
>> the AI points out.
> 
> I agree that is the point of the AI.
> 
>> > I am one of those who suspect that the new syntax would add more
> confusion
>> > than advantages to the language.
>> As I pointed out in an earlier post, this syntax exists in Ada already
>> for
>> protected types.  See, for example line 54 of phil.adb of the dining
>> philosophers
>> demonstration program that comes with GNAT:
>>
>>       Room.Sticks (First_Grab).Pick_Up;
>>
>> Room.Sticks (First_Grab) is the object; Pick_Up is the operation.
> 
> Well, I heard that protected types syntax was also subject of strong
> discussions and I can understand why.

Maybe because it is ugly? (:-))

Anyway prefix syntax exists also in the form of attributes. Strangely 
enough, that nobody has yet proposed to replace X'Length with X.Length. It 
would so OO-O-Oh! (:-))

> Nevertheless, protected types are
> declared in a different way than tagged types. They already encapsulate
> their subprograms and entries in their definition. Their syntax is more
> similar to that used for declaring classes in mainstream OO languages so I
> see natural to use the Object.Operation notation with protected types.
> Even in your example you have the name of the package (Room), so they do
> not "hide" the use clause.
> 
> However, primitive operation declarations of tagged types are encapsulated
> in the package as with any other kind of type and the syntax is inherently
> different. Why should we be able to use the new syntax only with tagged
> types?
> 
> Hmm... Maybe it should be the other way round and keep the tagged type
> syntax for protected types. I should propose "protected records" whose
> primitive operations were run in mutual exclusion... what to do with
> entries
> then?   :^)

Entries are just subprograms with queues. If an entry has several protected 
arguments then a call to it should start a protected action on both. As for 
implementation, it should be no problem in case single processor - single 
lock. For multiple processors, I do not know, anyway it will be never 
accepted. (:-))

Same for task entries. They also (unfortunately) have prefix syntax which 
prevents potentially interesting one-to-many rendezvous. And even more 
misterious entries of both a protected object and a task, sort of 
"protected rendezvous"! (:-))

--
As for prefix syntax, I would prefer an explicit renaming:

procedure Foo (X : T, Y : T);
procedure T.Foo (Z : T) renames Foo (X=>Z, Y=>with); -- (:-))

However prefix syntax is too often misleading. It is unusable for binary 
operations and multiple dispatching operations (if Ada would have them).

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