Re: The old "Object.Method" syntax debate

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

Robert I. Eachus wrote:

> Alexander Kopilovitch wrote:
>> Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:
>> 
>>>Anyway prefix syntax exists also in the form of attributes.
>> 
>> Yes, but attributes cannot be introduced by user -- sometimes programmer
>> can provide an implementation of an attribute, but isn't permitted to
>> introduce his own attribute... this is a privilege for language designers
>> and compiler vendors.
>> (An apostrophe often is no more visible that a dot, but its upper
>> position in the line suggests that the following attribute somehow came
>> from a high authority -:) .
> 
> I really don't like the idea of allowing the Object.Operation format to
> Ada.  Yeah, the compilers can usually figure it out understand it. But
> the potential confusion with component notation is going to confuse
> experienced Ada users.  (And eventually other O-O language users when
> the actually run into component references.

However it is also a step into abstract record types. Consider:

type Complex is private;
function Complex.Im return Real;
function Complex.Re return Real;

Here Complex appears a record type with read-only members Im and Re, being 
internally something else (a polar complex number).

> Since the language currently allows defining attributes which are
> procedures or functions, why not use the apostrophe notation?  Now the
> meaning of Object'Operation is clear, even when it is actually
> Object'Length or whatever.

To have X'Image instead of T'Image (X)? That is too good to become a 
reality. (:-))

> Probably need a rule about overloading
> predefined attributes, but that shouldn't be such a big deal.  (They
> would be non-overridable declarations in scope.)

Actually there should be an ability to declare/rename a subroutine in any of 
the following formats:

1. Functional: F (...)
2. Postfix: X.F (...)
3. Attribute: X'F (...)
4. Operational: X + Y
5. Index: X (...)
6. Aggregate: (...)
7. Constructor: X : T (...) and new T (...)

For both 2 and 3 the language should not allow other arguments be either 
dispatching or of the same type as the dedicated argument.

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