Re: [announcement] SYSAPI and SYSSVC for Windows

From: Ekkehard Morgenstern (ekkehard.morgenstern_at_onlinehome.de)
Date: 12/20/03

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    Date: Sat, 20 Dec 2003 20:52:30 +0100

    "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote:
    > The problem is to tell the customers, that *their* applications should be
    > designed so that *our* DLLs and hardware drivers would not stray into an
    > unpredictable state.

    What's the problem communicating this to the customer?

    > A manual reset event only needed when there could be more than one task
    > waiting for the event.

    Yes that, and then some. (sorry I don't have time right now to elaborate)

    > > C++ is well-defined also, btw. There's already a number of ISO standards
    > > for C and C++,
    >
    > A *number of* standards, fascinating! (:-))

    For Ada, there's also an '83 and a '95 rationale. ;)
     
    > Come on! C++ does not have:
    >
    > 1. multiple dispatch;

    True, except for constructors and destructors. They're always called for all derived classes of an object.

    Regular virtual methods have to call the methods of their parent class if so desired.

    > 2. dispatch on function result;

    True. Not possible w/ C++.

    > 3. dispatch on access types;

    False. Method overloading based on parameters of different types, even pointer types, is supported.

    > 4. differentiation between class-wide and specific types;

    Class-wide types in Ada roughly correspond to base classes in C++.

    > 5. functions returning class-wide objects on the stack;

    True, but you can return a reference to an object. (I'm not sure if passing a reference to a
    temporary object would work)

    > 6. streaming / object factory support ('Input, 'Output attributes in Ada);

    There are provisions for that in the C++ streams standard library. But I haven't yet read
    about the features in Ada you're talking about.

    > 7. formal derived type parameter for generics;

    False. Of course you can use derived classes or other types in templates.

    > Why? The following is OK:
    >
    > type T is limited private;
    > private
    > type T is limited record
    > I : aliased Integer;

    Yes, but I is an Integer. Discrete types can always be aliased.

    In my case, it was an array of aliased types, and I wanted to create an access
    to an array element.

    > "Aliased" is the keyword for that. Objects of some types are always
    > aliased:
    >
    > type T is tagged limited ...;

    so I could've just used a tagged limited record?

    Like this:

        type T is tagged limited
        record
            A : My_Array_Type;
        end record;

        procedure F ( O : in out T ) is
            Ptr : My_Array_Cell_Ptr;
        begin
            Ptr := O.A(1)'Access;
        end;

    Right?

    > And finally, if you want to get a pointer in F, then probably
    >
    > procedure F (O : access T);
    >
    > is reasonable.

    Unfortuantely I cannot pass this on to the entry points of my task. ;)

    So I decided to use a regular access types and Limited_Controlled types.

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