From: "Nick Roberts" <nickroberts@adaos.worldonline.co.uk>
Subject: Re: Sugestion to Multiple Inheritance
Date: Sat, 12 Jan 2002 00:28:44 -0000
Date: 2002-01-12T00:28:44+00:00 [thread overview]
Message-ID: <a1o2gv$sfe3f$4@ID-25716.news.dfncis.de> (raw)
In-Reply-To: slrna3tf3u.kg.lutz@taranis.iks-jena.de
"Lutz Donnerhacke" <lutz@iks-jena.de> wrote in message
news:slrna3tf3u.kg.lutz@taranis.iks-jena.de...
> I'm looking for a design glue to build something like this:
>
> I have an several (at least two) interfaces with must be implemented
> by the end user (compiler should require implementation). All of them
> build a free(!) depedency tree. The simplest one is:
>
> A -> B B is an extended A and C is an extended A.
> | | D combines both extensions (requiring both).
> v v
> C -> D
>
> There are (generic) packages requiring special interfaces.
>
> I'd like to use abstract types and class wide programming, but this can't
be
> done in Ada naturally.
Taking the following example similar to your situation:
type Respirant is abstract ...;
procedure Breathe (Animal: in out Respirant; Air: ...);
type Mammal is abstract new Respirant with ...;
function Lactate (Animal: in Mammal) return Milk;
type Arboreal is abstract new Respirant with ...;
procedure Climb (Animal: in out Arboreal; Tree: ...);
type Sloth is abstract new Arboreal, Mammal ...; --?
Maybe one solution is as follows:
type Sloth is abstract new Respirant with ...;
type Mammal_Aspect is access all Mammal'Class;
type Arboreal_Aspect is access all Arboreal'Class;
function As_Mammal (Animal: in Sloth) return Mammal_Aspect;
function As_Arboreal (Animal: in Sloth) return Arboreal_Aspect;
function Toes (Animal: in Sloth) return Two_Or_Three;
Thus, if you had:
type Two_Toed_Sloth_As_Mammal is new Mammal with ...;
-- implement Breathe and Lactate
type Two_Toed_Sloth_As_Arboreal is new Arboreal with ...;
-- implement Breathe (again!) and Climb
type Two_Toed_Sloth is new Sloth with
record
Mammalianness: aliased Two_Toed_Sloth_As_Mammal;
Arboreality: aliased Two_Toed_Sloth_As_Arboreal;
end record;
-- implement Breathe (yet again!!)
function As_Mammal (Animal: in Two_Toed_Sloth)
return Mammal_Aspect is
begin
return Animal.Mammalianness'Access;
end;
function As_Arboreal (Animal: in Two_Toed_Sloth)
return Arboreal_Aspect is
begin
return Animal.Arboreality'Access;
end;
function Toes (Animal: in Two_Toed_Sloth)
return Two_Or_Three is
begin
return 2; -- ;-)
end;
Jenny: Two_Toed_Sloth;
You could then make Jenny climb to safety:
Climb( As_Arboreal(Jenny).all, Nice_Tall_Tree );
Ugly, but it works, as they say. Hope this helps!
--
Best wishes,
Nick Roberts
prev parent reply other threads:[~2002-01-12 0:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-11 10:20 Sugestion to Multiple Inheritance Lutz Donnerhacke
2002-01-11 17:21 ` Stephen Leake
2002-01-11 17:53 ` Lutz Donnerhacke
2002-01-11 19:57 ` Stephen Leake
2002-01-17 8:28 ` Lutz Donnerhacke
2002-01-17 14:31 ` Stephen Leake
2002-01-17 14:54 ` Lutz Donnerhacke
2002-01-17 20:52 ` Jim Rogers
2002-01-11 18:07 ` Mark Lundquist
2002-01-11 18:14 ` Richard Riehle
2002-01-11 20:56 ` Hyman Rosen
2002-01-12 7:35 ` Richard Riehle
2002-01-13 6:37 ` Hyman Rosen
2002-01-14 13:58 ` John English
2002-01-14 16:27 ` Ole-Hjalmar Kristensen
2002-01-12 2:09 ` Will
2002-01-11 22:04 ` Matthew Heaney
2002-01-15 15:32 ` Hyman Rosen
2002-01-15 16:03 ` Lutz Donnerhacke
2002-01-18 19:03 ` Matthew Heaney
2002-01-21 11:23 ` Lutz Donnerhacke
2002-01-21 16:43 ` Brian Rogoff
2002-01-21 17:00 ` Lutz Donnerhacke
2002-01-22 16:55 ` Brian Rogoff
2002-01-23 8:58 ` Dmitry A. Kazakov
2002-01-25 0:09 ` Brian Rogoff
2002-01-28 16:23 ` Dmitry A. Kazakov
2002-01-12 0:28 ` Nick Roberts [this message]
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