[Oberon] Type compatibility in Oberon

[Jörg]

Chris

 

Thanks for bringing this up.

Now we are exactly at the heart of the problem.

Oberon as it is defined in the report leaves some parts needed for low level programming to the implementation.

There are some small but very important “cheats” in the compiler allowing to compile itself and the Oberon system.

If you implemented a strict compiler according to the Oberon report, the Oberon system and compiler would not compile.

 

NW likes to say: “Oberon is high level programming language but also well suited to low level programming. Proof: the compiler and the whole system can be written in Oberon”. This statement is only true if you use his compiler but not with his language according to the report!

 

Some cheats not defined in the Oberon report:
Allow assignment to INTEGER values of 32bit hex values. (FileDir.Search: the ASSERT would not compile without this cheat)
Allow BYTE n OF BYTE to be compatible with all types of same size (FileDir.Search: GetSector would not compile without this cheat)
 

br

Jörg

 

Von: Oberon <oberon-bounces at lists.inf.ethz.ch> im Auftrag von Chris Burrows <chris at cfbsoftware.com>
Antworten an: <chris at cfbsoftware.com>, ETH Oberon and related systems <oberon at lists.inf.ethz.ch>
Datum: Freitag, 1. Mai 2020 um 08:26
An: ETH Oberon and related systems <oberon at lists.inf.ethz.ch>
Betreff: Re: [Oberon] Type compatibility in Oberon

 

Thank you for the reference. However, I could not see anything there that stated that extensions to the language extensions had been included. An immediate problem that jumps out at me is rule G4:

 

f is a parameter of type ARRAY m OF BYTE and Ta is any type with size n = m bytes.

 

That rule is *not* part of the latest 2016 version of Oberon language definition (or any previous version AFAIR). You may have been misled by the fact that It is an undocumented feature that has been implemented in the RISC5 Oberon compiler. As I have stated here recently the RISC5 compiler should not be treated as if it were a language reference compiler.

 

Regards,

Chris Burrows

CFB Software

https://www.astrobe.com

 

From: Luca Boasso [mailto:luke.boasso at gmail.com] 
Sent: Friday, 1 May 2020 3:37 PM
To: chris at cfbsoftware.com; ETH Oberon and related systems
Subject: Re: [Oberon] Type compatibility in Oberon

 

For an up to date and comprehensive list of type rules for Oberon-07 you can also refer to:  https://github.com/lboasso/oberonc/blob/master/doc/TypeRules.md

oberonc slightly generalizes the implied rules in Prof. Wirth latest source code.

 

Comments like "(* Type Rule F.1, F.2 *)" clearly link the definition in the document with the actual implementation in the code, leaving little space for interpretation.

 

 

On Thu, Apr 30, 2020, 15:32 Chris Burrows <chris at cfbsoftware.com> wrote:

When I followed the link in the post below the item that really grabbed my
attention was the excellent document:

Type compatibility in Oberon

https://www.miasap.se/obnc/type-compatibility.html

It is apparent to me that a lot of thought has gone into the preparation of
this document. It would be very useful to any Oberon programmer who was
having difficulty understanding why his program would not compile due to a
type-compatibility issue.

I haven't used OBNC so can't say how well it conforms to these rules -
knowing August's great attention to detail I would expect it to be 'very
well'. While the Astrobe ARM compilers comply with the vast majority of
these rules there are one or two minor exceptions. These are described in
the accompanying documentation. You should also expect some very minor
relaxations of the rules (e.g. ARRAY OF BYTE parameters) when using the
Project Oberon RISC5 compiler. 

Regards,
Chris Burrows
CFB Software
https://www.astrobe.com



> -----Original Message-----
> From: Oberon [mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of
> August Karlstrom
> Sent: Friday, 1 May 2020 2:00 AM
> To: oberon at lists.inf.ethz.ch
> Subject: Re: [Oberon] Interfacing with Foreign Systems
> 
> On 2020-04-30 01:50, Skulski, Wojciech wrote:
> > Chris:
> >
> >    how about OOC and OO2C? Are they not in the same spirit?
> >
> > http://ooc.sourceforge.net/index.html
> 
> OBNC is a better example. It targets the latest version of Oberon and is
> actively maintained.
> 
> https://www.miasap.se/obnc/
> 
> 
> -- August
> --
> Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems
> https://lists.inf.ethz.ch/mailman/listinfo/oberon

--
Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems
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