[cl-store-devel] Incompatibility with Allegro CL 8.1

[Sean]

Hi Pawel,

 I'm busy merging in these changes into cl-store (sorry it's taken
 so long) and was  wondering what the actual error was when 
 loading the old code.

 The problem I've run into is that in ACL 8.0  
 #.EXCL::*NAN-SINGLE* is not eql to the result
 of   (/ (expt most-positive-single-float 3)
         (expt most-positive-single-float 3))
 which is causing 2 of the tests to fail.
 
 If 
 (eql #.EXCL::*NAN-SINGLE*
      (/ (expt most-positive-single-float 3)
         (expt most-positive-single-float 3)))

 returns true in ACL 8.1 then i'll conditionalize the 'magic' float
 numbers for pre ACL 8.1 and ACL 8.1
  
Cheers,
 Sean.

On Tue, 2007-05-15 at 13:34 +0200, Pawel Turnau wrote:
> > On Fri, 2007-05-11 at 20:07 +0200, iso at wemba.edu.pl wrote:
> >> cl-store_0.7.2 cannot be compiled with Allegro CL 8.1 (currently
> >> beta). I have contacted Franz Inc. and was told that the file
> >> acl/custom.lisp needs to be changed.
> >
> > Thanks for the patch, I'll take a look at it some time later today.
> 
> You may be interested to see the whole message from Duane Rettig from
> Franz Inc. (I enclose it below). I replied that #-allegro is probably
> unnecessary, since the file is only meant for ACL consumption anyway.
> 
> By the way, I changed cl-store as they recommended and I have been
> using it for the last couple of days. I haven't noticed any problems.
> 
> Pawel
> 
> 
> ================================================================
> >> Evaluating (expt most-positive-single-float 2) with ACL8.1b produces an error.
> 
> It is clear that your intention in evaluating this form is to
> explicitly generate infinities.  Unfortunately, the value that used to
> be returned from this form was not mathematically correct - since the
> value of most-positive-single-float is 3.4028235e+38 or approximately
> 3.402 x 10^38, and taking the square of that is approximately
> 1.158 x 10^77, and not infinity.  But since this value cannot be
> represented as a single float, it is an error to ask for it.  We used
> to respond to this error by simply returning an infinity, but to
> signal error is a better thing than to provide a wrong answer.
> 
> Now, to your problem at hand:
> 
> >> I am using the CL-STORE package:
> >> 
> >> =========
> >> README for Package CL-STORE.
> >> Author: Sean Ross 
> >> Homepage: http://www.common-lisp.net/project/cl-store/
> >> Version: 0.6
> >> =========
> >> 
> >> I cannot compile it with ACL 8.1 Beta, because the file
> >> acl/custom.lisp contains the following lines:
> >> 
> >> (defvar +single-positive-infinity+ (expt most-positive-single-float 2))
> >> (defvar +single-negative-infinity+ (expt most-negative-single-float 3))
> >> (defvar +single-nan+ (/ +single-negative-infinity+ +single-negative-infinity+))
> >> 
> >> (defvar +double-positive-infinity+ (expt most-positive-double-float 2))
> >> (defvar +double-negative-infinity+ (expt most-negative-double-float 3))
> >> (defvar +double-nan+ (/ +double-negative-infinity+ +double-negative-infinity+))
> >> 
> >> (setf *special-floats*
> >>   (list (cons +double-positive-infinity+ +positive-double-infinity-code+)
> >>         (cons +single-positive-infinity+ +positive-infinity-code+)
> >>         (cons +single-negative-infinity+ +negative-infinity-code+)
> >>         (cons +double-negative-infinity+ +negative-double-infinity-code+)
> >>         (cons +single-nan+ +float-nan-code+)
> >>         (cons +double-nan+ +float-double-nan-code+)))
> 
> Apparently, at least most lisps return an infinity for each of these
> erroneous expt calls, but I susopect that that won't be true for very
> long.  I suggest that you duplicate the 6 defvars and wrap them into
> the follwing pair of progns:
> 
> #-allegro
> (progn
>   (defvar +single-positive-infinity+ (expt most-positive-single-float 2))
>   (defvar +single-negative-infinity+ (expt most-negative-single-float 3))
>   (defvar +single-nan+ (/ +single-negative-infinity+ +single-negative-infinity+))
> 
>   (defvar +double-positive-infinity+ (expt most-positive-double-float 2))
>   (defvar +double-negative-infinity+ (expt most-negative-double-float 3))
>   (defvar +double-nan+ (/ +double-negative-infinity+ +double-negative-infinity+)))
> 
> #+allegro
> (progn
>   (defvar +single-positive-infinity+ excl::*infinity-single*)
>   (defvar +single-negative-infinity+ excl::*negative-infinity-single*)
>   (defvar +single-nan+ excl::*nan-single*)
> 
>   (defvar +double-positive-infinity+ excl::*infinity-double*)
>   (defvar +double-negative-infinity+ excl::*negative-infinity-double*)
>   (defvar +double-nan+ excl::*nan-double*))
> 
> These symbols are unexported, and thus undocumented and unsupported,
> but they have never changed, and their meaning should be obvious.  I
> will file an rfe to consider exporting them.  Meanwhile, you might
> want to communicate with Sean Ross, the developer of the project, and
> let him know what is happening.  It would be premature to make the
> change permanent, especially if we come up with a way to provide
> infinities and nans through supported means, but the above technique
> should at least work for now, and is likely to remain compatible with
> any change we make in the future.
> 
> Let me know if you have trouble with this technique.
> 
> Duane Rettig    duane at franz.com    Franz Inc.  http://www.franz.com/
> 555 12th St., Suite 1450               http://www.555citycenter.com/
> Oakland, Ca. 94607        Phone: (510) 452-2000; Fax: (510) 452-0182   
> 
> ================================================================
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