[Oberon] System.Directory options

Andreas Pirklbauer andreas_pirklbauer at yahoo.com
Wed Nov 1 20:58:15 CET 2017

> On a more general basis, the character "!" was clearly a
> hack. It was meant an as exception to otherwise clean rules.
> Apparently, clean rules led to restrictions, and the real
> life prevailed.

Yes, it’s always been a hack - and one that got worse over
time, not better, unfortunately. Back in 1988 there was in
fact no ! option. Then an option stored in a global variable
diroptions was added pretty soon by someone. See the 1992
and 2005 Editions of the book Project Oberon, which state:

  PROCEDURE List(..);
    IF diroption = "d” THEN      (*<--- global variable*)
      Kernel.GetSector(adr, hp);
      Texts.WriteString(W, " “);
      Texts.WriteDate(W, hp.time, hp.date);
        + hp.bleng - FileDir.HeaderSize, 8)
  END List;

  PROCEDURE Directory*;
    i := 0;
    WHILE (ch > " ") & (ch # "/") DO
      pat[i] := ch; INC(i); Texts.Read(R, ch)
    pat[i] := 0X;
    IF ch = "/“ THEN
       Texts.Read(R, diroption)  (*<—global variable*)
    ELSE diroption := 0X
  END Directory;

So the option was a variable ‘diroptions’ and not
yet packed into the pattern ‘pat'.

Then suddenly someone had the idea to pack the ! option
into the pattern itself (which is still the current
status quo), thereby eliminating the global variable
diroptions. Why was it done this way? I have no idea!

The clean solution would be:

1) to return to the original 1992/2005 approach with
   a separate variable diroptions.

2) to generalize procedure System.GetArg such that
   also accepts Unix style parameters -a, -b ..

All this exists in various places and in various
forms, e.g. regular expression parsers in Native
Oberon. It just isn’t part of Original Oberon -
which is a pity.



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