November 2019 - Oberon - mailman3.inf.ethz.ch

Wanted: Oberon Syntax in TextMate, Sublime Text or Atom Grammar
by Treutwein Bernhard 01 Jan '22

01 Jan '22

Does somebody have grammars for Oberon / Oberon-2 / Component Pascal / Active Oberon as grammar for TextMate / Sublime Text / Atom Background: Github wrongly classifies Oberon / Oberon-2 / Component Pascal / Active Oberon as Modula-2. I opened quite some tiome ago an issue in the github/linguist project (https://github.com/github/linguist/issues/3888) and they don't accept EBNF grammars. -- Bernhard Treutwein

6 9

Debugging FPGA oberon via serial line?
by Michael Schierl 29 May '20

29 May '20

Hello, while I was adding UTF-8 support to Fonts and Texts (and almost rewriting Fonts so that a font can be loaded partially and not all glyphs at once), I noticed that debugging such a system can be cumbersome (as you cannot read the TRAP output any more, as well as you have to reset the system to a previous state to be able to fix your mistakes if the screen is too garbled to be useful, or if the system TRAPs during boot). By the way, here is Oberon running in the browser with UTF-8 support for Texts (and Tahoma font): http://schierlm.github.io/OberonEmulator/emu.html?image=UnicodeDiskImage >From other (older) systems, I know it is possible to debug them via serial line, so I was thinking how much the FPGA oberon system needs to be changed (hardware side/software side) to accommodate this. RS232 is supported, so you could use one FPGA system (or emulator) to debug the other one. And I was wondering if anybody already tried doing something like this. I know that Colby Russell worked on debug support in the emulator, but no idea about how far he got. A minimal feature set to be useful (in my opinion) would be - Read and write memory and disk via serial port while the system is running/idle (already possible today via ORC / PCLink) - Set and remove software breakpoints while the system is running/idle - When software breakpoint or trap is hit, save processor state and allow debugging via serial port (-> suspended) - Read and write registers and memory while the system is suspended - Set and remove software breakpoints while the system is suspended - Continue execution when the system is suspended More advanced features would be single stepping (can be emulated by having a look at the instruction and setting software breakpoints at all following locations), or memory breakpoints. Also to be able to enter the debugger by pressing a hardware button on the FPGA (similar to the current reset functionality, but not resetting). And of course symbolic debugging :) Software breakpoints should be easy, just replace instruction by BL to a fixed address. Restore the instruction before returning. For catching TRAPs, overwrite the TRAP address. Saving processor state might be tricky, especially SYSTEM.H and the flags, and maybe you have problems since you need at least one spare register to be able to save the registers to a fixed location in memory. You will also need to switch stack to a second stack before the stack is accessed by the code. Probably solvable by using a special compiler that leaves a register or two unused. Restoring SYSTEM.H and Flags is also not supported (except by searching for instructions that will result in the desired flags or results). Also the question is whether returning to the code will not destroy some flags again. And you need to make sure not to set breakpoints or break at points where a BL has happened but the link register has not been saved yet. So (similar to interrupt) probably some hardware support is needed for this. Entering the debugger by button also needs hardware support (since the current Reset button forgets the PC and some other state). Once in suspend mode, it might be hard to avoid allocating memory, since you cannot run the GC which might collect objects that are still used by the suspended program. But that should be feasible if the functions are basic enough to work with a fixed buffer (e.g. number of breakpoints is limited). I guess memory breakpoints are only possible with hardware support for them (I have no idea how to emulate them except emulating or setting breakpoints at all LOAD/STORE instructions). For symbolic debugging, the compiler would have to write some more debug symbols. For a start, <https://github.com/schierlm/OberonXref/blob/master/ORG.Mod.patch> annotates the code position for every instruction; I currently use it for creating combined source/assembly listings like <https://schierlm.github.io/OberonXref/ProjectOberon2013/ORP.html#both>. But you would probably also need some information about the stack layout (variable names and types) and register contents for every code locatoin, as well as information about module/global variables, and not-exported record types and record members. And you would also need some client to utilize all this information so that you can do something like "Debugger.Inspect F.vwr.dsc" :) So I guess for my own needs, that's too much work for the benefit (especially since I don't know if I will ever try to rewrite any of the core modules again). But perhaps I'm missing something? Any better ideas? Regards, Michael

1 1

A2 Repository
by peter＠easthope.ca 13 Apr '20

13 Apr '20

Hi, rev.9527 on Guenter's Web site is dated September 26. >From felix.friedrich ... Wed Jul 3 09:30:57 2019 > We are currently investing effort into cleaning up A2 ... > ... > ... we will make sure that native versions are properly supported again. > ... need to finish this work before October. Are native versions suitable for end users now? Hold off a little longer? Thanks, ... Peter E. -- https://en.wikibooks.org/wiki/Medical_Machines Tel: +1 604 670 0140 Bcc: peter at easthope. ca

3 4

Re: [Oberon] Oberon online (code snippets sharing)
by peter＠easthope.ca 19 Dec '19

19 Dec '19

From: Erik Terpstra <erterpstra(a)gmail.com> Date: Tue, 13 Aug 2019 10:00:04 +0200 > I have asked the maintainer of tio.run (Try It Online, a code snippet > sharing site) if Oberon-07 could be added, he agreed and added support for > it (using the OBNC compiler). Thanks Erik. > You can see a Hello world snippet here: > > https://bit.ly/2Mic0NN A click on Oberon-07 in the list of languages leads to https://tio.run/#oberon-07 . Is there any harm in referring to that URL? Thanks, ... Lyall E. -- https://en.wikibooks.org/wiki/Oberon Tel: +1 604 670 0140 Bcc: peter at easthope. ca

6 8

Re (2): Updating a Text in a Gadget.
by peter＠easthope.ca 30 Nov '19

30 Nov '19

From: Joerg <joerg.straube(a)iaeth.ch> Date: Wed, 27 Nov 2019 19:28:58 +0100 > Please have a look at chapter 5 (and especially chapter 5.3) of this Oberon Guide: > https://inf.ethz.ch/personal/wirth/ProjectOberon/PO.System.pdf Thanks. I've reviewed that and the parallel section in the earlier edition. 1992, 2005 edition, chapter 5, Text. "Update Msg = RECORD (Display.FrameMsg) id: INTEGER; text: Texts.Text; beg, end: LONGINT END; Field id names one of the operators replace, insert, or delete. The remaining fields text, beg, and end restrict the change to a range." 2013 edition "UpdateMsg = RECORD (Display.FrameMsg) id: INTEGER; text: Texts.Text; beg, end: INTEGER END;" Source in A2O (A2, Oberon subsystem). "UpdateMsg* = RECORD (Display.FrameMsg) (** Message broadcast to indicate that part of a text changed. *) text*: Text; (** The text that changed. *) beg*, end*, len*: LONGINT (** Change location. *) END;" The need for begin and end is understandable. If a small segment of a large Text is revised, there is no point in updating the whole Text. The segment to update is specified by begin and end. I'm trying to understand len, which is in A2O and probably in S3; not in Oberon. A simple assumption is len = end - beg. No; there's more to it than that. I've glanced at a calculation involving beg, end and len but not made sense of it yet. The explanation might be obvious to others or might be explained in the Mueller thesis. Haven't checked there yet. Any idea appreciated, thanks, ... Lyall E. -- https://en.wikibooks.org/wiki/Medical_Machines Tel: +1 604 670 0140 Bcc: peter at easthope. ca

2 1

Updating a Text in a Gadget.
by peter＠easthope.ca 27 Nov '19

27 Nov '19

GIVEN Text T in a Doc viewer or Gadget is changed by Texts.Replace(T, begin, end, buffer). OBSERVATION The appearance of the Text can be changed by Replace. For example, if Store is executed and the Text is opened again from the file, the new view can differ from the view before Replace. QUESTION How should the view of the Text in the original viewer be updated without storing to a file and opening again? Can the frame be updated after Replace? Make the change with something other than Texts.Replace? Thanks, ... Lyall E. -- https://en.wikibooks.org/wiki/Medical_Machines Tel: +1 604 670 0140 Bcc: peter at easthope. ca

2 1

Active Oberon language - a question regarding scope rules
by Andreas Pirklbauer 21 Nov '19

21 Nov '19

> maybe that question would better be posted in the forum > at http://cas.inf.ethz.ch/projects/a2/boards to give it some life Thanks. Done. And already answered: Active Oberon DOES indeed implement "shadowing through scope”.

1 0

[Oberon ] Active Oberon language - a question regarding scope rules
by Andreas Pirklbauer 21 Nov '19

21 Nov '19

> ETH (Active) Oberon Language Report > > Added by Felix Friedrich about 1 month ago > > Although it is work in progress, we have decided to publish the current state of the ETH > Oberon Language Report together with the tools in the A2/Oberon repository. > > It can be found here: export:/trunk/LanguageReport/OberonLanguageReport.pdf > The above Active Oberon language reports states on p.12 (“Declaration and Scope Rules”): “An item may be directly referenced within its scope only." QUESTION: Does this mean that Active Oberon implements "shadowing through scope”? I.e. does an intermediate variable (such as the intermediate variable g declared in P below) block access to a global variable with the same name from within a nested scope Q? MODULE M; VAR g: INTEGER; (*global variable g*) PROCEDURE P*; VAR g: INTEGER; (*DOES this intermediate variable “shadow” (=block access to) the global variable g?*) PROCEDURE Q; BEGIN g := 1 (*OR can a nested procedure Q still access the global variable g here??*) END Q; BEGIN Q END P; END M. For example, in Oberon-07 this leads to a “pos 195 inaccessible” compile time error, so Oberon-07 DOES implement shadowing through scope. Historically, most Algol-like languages have traditionally implemented shadowing through scope. However, in the earlier languages (Algol, Pascal, Modula, Oberon 1988) access to surrounding scopes was actually ALLOWED, so the shadowing concept made perfect sense. But in Oberon-07 (and Active Oberon I suppose) intermediate variables can no longer be accessed from within nested scopes. So the question is whether shadowing still has its place in such languages or whether it should be abolished. Allowing access to the global scope - regardless of whether intermediate variables with the same name exist or not - would effectively make nested procedures self-contained in the sense that they can be moved around freely. For example, procedure Q could now be made local to procedure P without having to worry about whether one can still access the global variable g or not (as the scope of P is simply ignored). -ap

2 1

ETH (Active) Oberon Language Report 2019
by Liam Proven 20 Nov '19

20 Nov '19

http://cas.inf.ethz.ch/news/2 « ETH (Active) Oberon Language Report Added by Felix Friedrich about 1 month ago Although it is work in progress, we have decided to publish the current state of the ETH Oberon Language Report together with the tools in the A2/Oberon repository. It can be found here: export:/trunk/LanguageReport/OberonLanguageReport.pdf (We moved the comments into the forum: ETH (Active) Oberon Language Report) » -- Liam Proven - Profile: https://about.me/liamproven Email: lproven(a)cix.co.uk - Google Mail/Hangouts/Plus: lproven(a)gmail.com Twitter/Facebook/Flickr: lproven - Skype/LinkedIn: liamproven UK: +44 7939-087884 - ČR (+ WhatsApp/Telegram/Signal): +420 702 829 053

5 7

fye: presentation Why Isn't Functional Programming the Norm? – Richard Feldman
by Frans-Pieter Vonck 19 Nov '19

19 Nov '19

For your entertainment. Feldman makes an interesting analysis how the top 10 programming languages became so popular Half way he makes a comparison between Go and Modula. Although he does not mention Go and states that C is invented out of annoyance over Pascal, it is still an entertaining talk about programming language paradigms. Here he compares Go to Modula https://youtu.be/QyJZzq0v7Z4?t=1300 Greets, Frans-Pieter

1 1