(j3.2006) (SC22WG5.5350) From a colleague

[Bill Long]

On Oct 27, 2014, at 2:57 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:

> My colleague wrote:
> 
>        I've just learned that at least some compilers will no longer
>        support the arithmetic IF statement.  The reason being that


It would be interesting to know what compiler vendors are telling him this.   I assume ones claiming Fortran 2015 conformance, since if they are claiming Fortran 2008 or earlier conformance arithmetic IF is still required.  Or maybe those vendors are not claiming conformance to any standard. 



>        there is no good  answer as to what this statement should do if
>        the value in question is a NaN.  And here I thought that
>        compiler writers would continue to support all the old features
>        out of self interest.  But here there seems to be no good
>        answer.
> 
> -------------------------------------------------------------------------
> 
> This colleague has "only" about 170,000 lines of Fortran 77 code to
> support.  He's a semi-retired proprietor of a small business, with no
> staff other than himself to revise his codes so as not to use Arithmetic
> IF.  I don't know how many clients are using his software.

F77 already had better IF constructs than arithmetic IF.  This really sounds like F66 code. 

I?d guess that there will still be compilers available for quite some time that will work with his code.  While 170,000 lines is not that large compared to a lot of codes, trying to figure out the intended control logic implemented with all those arithmetic IF statements could be time consuming.   

> 
> I'm expecting that people who use a library of mathematical software on
> which I worked, from 1974 until support was discontinued in 1996, will
> experience the same problem.  At one time, we had 600 users.  I don't
> know how many people still use it.


Well, I guess that is what ?support was discontinued? implies. Especially when it was 18 years ago.   I assume development of the code stopped many years before support was discontinued.  By the 90?s  there were way better control constructs available.


> 
> Was it really wise, and especially was it necessary, to delete
> Arithemtic IF?  Couldn't we just leave it in obsolescent font?

That?s a WG5 decision for the London meeting. 

Cheers,
Bill



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Bill Long                                                                       longb at cray.com
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