[M3devel] assignability of fixed and open arrays, was: RE: release engineering 5.8: code generator error for IP address initializers

[Olaf Wagner]

Quoting Jay K <jay.krell at cornell.edu>:

> (back to the topic :) )
>
> somewhat reduced case:
>
> MODULE Main;
>
> TYPE T1 = ARRAY [0..0] OF INTEGER;
>
> CONST const: T1 = ARRAY OF INTEGER{2};
> BEGIN
> END Main.
>
> The problem is two global integers are overlapping.
> The open array size and its first element.
>
> Are these syntaxes legal?
> This apparent mixing of open and fixed arrays?

You mean it would work for

   CONST const: T1 = ARRAY [0..0] OF INTEGER{2};

The type of const is no open array, but the fixed array A1.
So the question would be: is an open array (of the correct size)
assignable to a fixed array type?

   An expression e is assignable to a variable v if:

     * the type of e is assignable to the type of v, and
     * the value of e is a member of the type of v, is not a local procedure,
       and if it is an array, then it has the same shape as v.

though this is not a variable assignment, but a constant definition.
Nonetheless, if that's assumed to be equivalent, then it would depend
on the definition of shape: does it include the length field or not?

I'd tend to think it does not (since that's just a representation the
compiler (writer) chose), but only the number of dimensions and elements
should count.

But this is certainly subtle and others may see it differently.

Olaf
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