A new notion: stronglly-typed-by-user language
in [ADA]
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From: Maciej Sobczak on 16 Apr 2010 16:50 On 16 Kwi, 22:20, "J-P. Rosen" <ro...(a)adalog.fr> wrote: > Maciej Sobczak a écrit :> So which C++ language features exactly make it not strongly typed? > > 1) Lack of user-defined elementary types This is addressed by: http://www.msobczak.com/prog/typegen/ Alternative solutions involve templates or preprocessor or even hand- written classes with appropriate operations - all of them are purely C+ +-based. > 2) Type promotion I don't see how type promotion violates the strong type safety. In particular, type promotions are used in read-only operations (that is, type is promoted when the value is read, not when it is written), so they do not modify the state of the object that is subject to promotion - as such, they do not subvert the type system in any way. What about promoting integer values to Type'Base in arithmetic operations? Isn't it a form of type promotion? -- Maciej Sobczak * http://www.inspirel.com YAMI4 - Messaging Solution for Distributed Systems http://www.inspirel.com/yami4
From: Pascal Obry on 16 Apr 2010 16:53 Le 16/04/2010 19:24, Dmitry A. Kazakov a �crit : > BTW, the Ada's OO kernel has this same design flaw. You can clone all > types, but tagged: > > type Count is new Current; -- This is OK only if Current is not tagged! type Count is new Current with null record; Pascal. -- --|------------------------------------------------------ --| Pascal Obry Team-Ada Member --| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE --|------------------------------------------------------ --| http://www.obry.net - http://v2p.fr.eu.org --| "The best way to travel is by means of imagination" --| --| gpg --keyserver keys.gnupg.net --recv-key F949BD3B
From: Dmitry A. Kazakov on 16 Apr 2010 17:51 On Fri, 16 Apr 2010 22:53:04 +0200, Pascal Obry wrote: > Le 16/04/2010 19:24, Dmitry A. Kazakov a �crit : >> BTW, the Ada's OO kernel has this same design flaw. You can clone all >> types, but tagged: >> >> type Count is new Current; -- This is OK only if Current is not tagged! > > type Count is new Current with null record; That would not create an unrelated type, the class is same. function "+" (Left : Current; Right : Current'Class) return Current; X : Current; Y : Count; begin X := X + Y; -- No type error -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: J-P. Rosen on 17 Apr 2010 01:25 Maciej Sobczak a �crit : > On 16 Kwi, 22:20, "J-P. Rosen" <ro...(a)adalog.fr> wrote: >> Maciej Sobczak a �crit :> So which C++ language features exactly make it not strongly typed? >> >> 1) Lack of user-defined elementary types > > This is addressed by: > > http://www.msobczak.com/prog/typegen/ This shows that an educated Ada programmer, well aware of the issues of strong typing, can mimmic the same behaviour in C++. But how many C++ programmers use that? >> 2) Type promotion > > I don't see how type promotion violates the strong type safety. Type promotion is based on the underlying representation, not on abstract types. And it is a form of automatic type case - which is always a bad idea IMHO. Note that T'Base is the same type as T, so there is no issue here. -- --------------------------------------------------------- J-P. Rosen (rosen(a)adalog.fr) Visit Adalog's web site at http://www.adalog.fr
From: Dmitry A. Kazakov on 17 Apr 2010 03:00
On Sat, 17 Apr 2010 07:25:25 +0200, J-P. Rosen wrote: > Note that T'Base is the same type as T, so there is no issue here. But it is not all same. The behavior of T'Base may differ, so it might be unsafe to use one as an equivalent of another in certain contexts (substitutability violation). -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de |