Re: Discriminants of tagged types

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 29 Paź, 20:59, "Vinzent Hoefler" <nntp-2010...@t-domaingrabbing.de>
wrote:

> > Just like a file descriptor. Yet, there is no reason for these things
> > to be polymorphic.
>
> But they already are.
>
> Sometimes they are files, sometimes devices, sometimes sockets, ...

No. File descriptors are just indices into some array of objects
managed by the operating system. Just plain integers, like here:

type Descriptor is Integer range 0 .. SOME_MAX;  -- this is what you
see

type Array_Of_Files_Managed_By_System_And_Hidden_From_You is
   array (Descriptor) of File'Class;

The actual objects are hidden from you and guess what? They have
polymorphic behaviour (sometimes they behave like files, sometimes
like devices and sometimes like sockets), but they are not themselves
copyable.

--
Maciej Sobczak * http://www.inspirel.com