[Oberon] Clarifying type compatibility in Oberon-07

[Andreas Pirklbauer]

> On Thu Oct 5 12:52:20 CEST 2017 Jörg joerg.straube at iaeth.ch wrote:
> Assignment rule 1 uses „same type". The things NOT covered by „same type“ are mentioned explicitly with own assignment rules.
>
> 4. Ta and Tb are pointer types whose pointer base types are the same, or
> This rule is not needed, as it is covered by Assignment rule 4, assuming T is an extension of T itself.
> 5. Ta and Tb are procedure types whose formal parameter lists match.
> This rule is not needed as it covered by Assignment rule 7.
> 
> br
> Jörg

Ok. So these two proposed rules are not needed (assuming T is an extension of T itself - which is the case, if I interpret the language report correctly).

While we are at it, what about the following similar rules for arrays (changes are marked with an asterisk * below). Would these be covered by the existing type rules and/or can these be derived from the language report? If these rules cannot be derived from the language report, should the language itself be extended?

Same Types
Two variables a and b with types Ta and Tb are of the same type if
....
*4. Ta and Tb are array types with same element types and lengths

Assignment compatible

An expression e of type Te is assignment compatible with a variable v of
type Tv if one of the following conditions hold:
....
*8. Tv is ARRAY OF Ta, e is ARRAY OF Tn, where Ta and Tb are the same types

-AP
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.inf.ethz.ch/pipermail/oberon/attachments/20171005/5c5fe72b/attachment.html>