(j3.2006) what now, 754r? - DFP in F2008?

[Jim Xia]

Hi Stan

To be clear I don't have any problems with DFP in FORTRAN standard since 
there are already hardware supports for DFP.  What I believe is the 
current standard that relies on SELECT_REAL_KIND intrinsic to return a 
KIND type parameter to designate a DFP type is awfully wrong.  In 
particular I dislike the rules in chapter 7 describing the operations 
involving DFP and other fp types.  In many cases, the kind type parameter 
of the result of such an operation is processor dependent.  This will for 
sure result in non-portable behavior on evaluation of an expression, which 
I can hardly imagine being useful at all to a user.  I'd prefer to the 
introduction of an extra type parameter, say RADIX, in real type so it can 
be used directly to designate a floating point that is not binary format. 
The rules in evaluation of expression should be further fine-tuned to 
specify behaviors when two floating points of different radix are involved 
in an expression.  Of course, there are many other details you need to 
work on, e.g. writing DFP literals, etc.

Given that F2008 is already on its final stage in publication, such a 
change is certainly not containable.  Therefore I prefer to having DFP 
feature converted to a TR rather rushing it in F2008.

Thanks,


Jim Xia

XL Fortran Compiler Testing
IBM Toronto Lab at 8200 Warden Ave.
Phone (905) 413-3444  Tie-line 969-3444
D2/NAH/8200 /MKM



"Whitlock, Stan" <stan.whitlock at intel.com> 
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09/14/2007 09:37 AM
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Re: (j3.2006) what now, 754r? - DFP in F2008?






Well, Jim, I don?t know if it makes sense to put DFP into Fortran 2008. Is 
IBM putting DFP support into xlf?  If so, what does it look like and how 
does it play with the rest of the data types?
 
/Stan

From: j3-bounces at j3-fortran.org [mailto:j3-bounces at j3-fortran.org] On 
Behalf Of Jim Xia
Sent: Thursday, September 13, 2007 9:31 PM
To: fortran standards email list for J3
Cc: WG5 List
Subject: Re: (j3.2006) what now, 754r?
 

Hi 

One thing comes to my mind right now is decimal floating point arithmetic. 
 Does it make sense for FORTRAN to have DFP in F2008? 

Thanks, 

Jim Xia

XL Fortran Compiler Testing
IBM Toronto Lab at 8200 Warden Ave.
Phone (905) 413-3444  Tie-line 969-3444
D2/NAH/8200 /MKM 
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