(j3.2006) (SC22WG5.4774) [ukfortran] [Letter ballot 3 on Fortran 2008interpretations]

[N.M. Maclaren]

On Sep 14 2012, Malcolm Cohen wrote:

>Van Snyder wrote:
>>My most fundamental objection to the interpretation is that it is
>>inconsistent with the requirements of 4.1.2, 4.2, and 13.7.2.  According
>>to 4.1.2 and 4.2, A type is characterized by a kind type parameter.  The
>>type and kind type parameter value together specify a set of valid
>>values.  According to 13.7.2, a function is required to return a value
>>that is a member of the set of valid values for the type and kind of its
>>result.  The interpretation violates this requirement.
>
> That is simply not the case. That is not what 13.7.2 says. either before 
> or after other interps changed that wording.

I am fairly good at seeing multiple interpretations, but I must say that
I have some difficulty finding one compatible with Van's.  However, I
do find it hard to be sure EXACTLY what 13.7.2 does specify.

> Furthermore, even if it did, such an interpretation of the "valid values" 
> wording would not result in "better answers" but (in the vast majority of 
> cases) worse answers, quite apart from the effects on optimisation.

I agree.  But this is another example of the concerns that some of us have
about the increasing problems that the concept of "what is a value?" is
causing.  Inter alia, this is because the prevailing views of what both
computational reals and floating-point are have changed drastically since
1977, but without the main standards (including IEEE 754) defining their
abstract models precisely enough to resolve such questions.  The LIA-x
standards did, but unfortunately lost the politics.

In my view, these issues are too pervasive and difficult to be solved by
interpretations, but do need addressing.  And, yes, I accept that I had
better write a proper paper if I want that done :-(


Regards,
Nick Maclaren.