[Oberon] Assumed issue in the Lola-2 compiler

Skulski, Wojciech skulski at pas.rochester.edu
Sun Apr 14 18:20:16 CEST 2019


yes, I know the design assumptions. I know that mixing the signed and unsigned types can lead to a nightmare. An example is provided in VHDL where I can import both signed and unsigned libraries, and of more than one kind at the same time. I did this in the past and I learned it is better avoided.

So maybe I should revert my comment and rather say that SET should be used for unsigned bit manipulation, while INTEGER and LONGINT (now being the same) is for math. But this is not a realistic position, either, as shown by this discussion. We are all conditioned to know how many bits the INTEGER has. As soon as there is a legitimate need for a 32 bit entity, we will throw in an INTEGER rather than a SET. But in this case the intent was a bit field rather than algebra, so INTEGER should not have been used. 

Is anyone going to be such a purist and start using SETs? You will probably agree that in practice we will all opt for INTEGERs. So there is a disconnect between a preferred practice and the envisioned intent behind both types. LOLA is an example which is more directed towards bit manipulation than math. Therefore, SETs should have been used, but they were not. It is a hint that perhaps the language is too minimalist in this case.


@Wojtek, as you know, Oberon-07 is intentionally a minimalist language,
in reaction, for example, to Modula-2, where Prof. Wirth rues that he
was persuaded to add too many features, types etc..  So please give an
example of where unsigned types are "necessary" and what that even
means, so we can have a sensible discussion.  Thanks!

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