(j3.2006) J3/12-nnn J3 interpretations letter ballot #26 aftermeeting 198

[Van Snyder]

On Fri, 2012-09-14 at 13:52 +0900, Malcolm Cohen wrote:
> Van Snyder writes:
> >          Since the only alternatives for <variable> are <designator>
> >          and <expr>, it seems weird to have <variable> in the syntax
> >          rule, and then a constraint that says it is required to be
> >          <designator>, not <expr>.
> ...
> >          If for some reason that doesn't work,
> 
> Obviously doesn't work because a <designator> is not necessarily a <variable>.
> 
> Use of <variable> with
> Cxxx The <variable> shall be a <designator>.
> 
> is not obviously worse than
> use of of <designator> with
> Cxxx The <designator> shall not be a constant or a subobject of a constant.

OK, I overlooked the necessity to duplicate C601.  Instead of the
proposed repair, an alternative is to add a syntax rule, instead of a
constraint that says "you can only choose the first alternative for the
syntax rule in this circumstance:"

[6.2 117:12-14]
R602 <variable> <<is>> <variable-designator>
                <<or>> <expr>

R602a <variable-designator> <<is>> <designator>

C601 (R602a) <designator> shall not be a constant or a subobject of a
constant

and move C602 above R602a, since it continues to apply to R602.

Then in R536 use <variable-designator> instead of <variable>, and make
the corresponding changes in the related constraints.