(j3.2006) READ unit ambiguity

[Van Snyder]

On Fri, 2012-03-02 at 05:26 -0800, Bill Long wrote:
> 
> On 3/2/12 1:05 AM, Van Snyder wrote:
> > Malcolm Cohen wrote:
> >>> In a new post, Ian Harvey
> >>
> >> Who is this guy? I hope you've invited him to join the committee!
> >>
> >>> points out that Note 3.7 is
> >>> no longer true. We can now have
> >>>
> >>> 10 .op. p = x
> >>>
> >>> where 10 can be a label or a left operand.
> >>
> >> Now this one is very easily fixed - just delete free-form source and
> >> the problem goes away.
> >
> > I obviously wasn't thinking of this case, but I did suggest, sometime
> > prior to 1986, that both statement labels and construct labels ought to
> > be followed by a colon in free form.
> 
> A bit too late for that.  However, we could (somewhat artificially) 
> disallow a statement number on a statement that looked like this. 
> Considering that statement numbers rarely show up in newer codes, I 
> would not expect much problem with backward compatibility.

The standard doesn't establish an unambiguous interpretation for this
statement, so it's not standard conforming.  It can be made conforming:

(10 .op. p) = x

or

10 (.op. p) = x

Alternatively, we could write an ugly constraint on assignment to
require the parentheses if the .op. is accessible in both unary and
binary forms, and the unary form has a first argument of integer type.
Ugh.  Or always.  Equally ughly.


> 
> Cheers,
> Bill
> 
> 
> >
> >> Cheers,
> >
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