On Wed, 13 Apr 2016, Maciej Izak wrote:
Moved from: "Initialize/Finalize management operators and Default
intrinsic". I'd like to keep Initialize/Finalize topic more clear ;P
Small introduction:
for selected language elements in Delphi is possible to use attributes. For
example in Delphi we have:
TCustomAttribute = class(TObject)
end;
WeakAttribute = class(TCustomAttribute);
UnsafeAttribute = class(TCustomAttribute);
RefAttribute = class(TCustomAttribute);
VolatileAttribute = class(TCustomAttribute);
which is used like this:
procedure Foo([ref] const X: TFoo); // AFAIK FPC equivalent is procedure
Foo(constref X: TFoo);
or like this for TObject field for ref. count for ARC:
[Volatile] FRefCount: Integer;
Sorry. This is simply very bad design.
1. We already have a syntax for this kind of thing, it is called modifiers.
No need to introduce a second syntax. You just introduce extra modifiers.
2. You make the COMPILER dependent on USER-DEFINED classes.
What kind of nonsense is that ?
It is even worse than the enumerator syntax Borland/Embarcadero invented.
If the compiler needs to know about it and act on it (and it does for ARC),
then it must be a keyword or modifier.
Attributes are meant for user-space information.
The compiler has no business with it, from the point of view of the compiler
the presence or non-presence of attributes is entirely irrelevant. It is
meant to be extracted easily by the user. No more, no less.
Attributes used like this are self-contained. You can use it or not, it
makes no difference to the compiler. This is an example of _good_ design.
If you use attributes to start controlling ARC or whatever other
_language feature_, this is _bad_ design, because you link one
feature to another, which simply is not related to it at all.
To clarify: I am not a big fan of the attributes syntax. But...
If attribute is used you already know that it has more "flag idea" (by
analogy to RTTI attributes, anyway it does not have to be just like a
flag), as in our example presented in "Initialize/Finalize management
operators and Default intrinsic" topic - is more visible whole context.
Introducing many new keyword is the waste and can collide with existing
keywords.
Clearly, you are missing something very important: Modifiers are _not_ keywords.
You can add as much modifiers as you want. They will never interfere with the
syntax.
That is the whole point of modifiers ?!
Michael.
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