Re: [Sbcl-devel] Printing/reading INF and NaN without #.

[James Y K. <fo...@fu...>]

On Nov 12, 2005, at 12:34 PM, Dan Corkill wrote:
> SBCL currently uses read-time evaluation (#.) forms to textually  
> represent
> infinite values.  We needed to be able to print/read these values  
> without
> *read-eval* enabled.  Lispworks uses a simple, extended number
> syntax to encode IEEE 754 values (e.g., 1e++0 for INF) that we like  
> and
> would like to see more broadly adopted.  Modified SBCL 0.9.6
> functions that provide this extended-syntax support for INF, -INF,
> and NaN can be found at:
> http://dancorkill.home.comcast.net/sbcl-inf.lisp
> (Sorry, I don't have these as patches to the development sources.)

1e++0 and -1e++0 seem like really bad representations for +-inf, as  
they are completely meaningless to most anyone who might see one.  
That 1e+-0 is the representation for NaN doesn't make things any  
better. And what's with only outputting the trapping-ness of the NaN  
in a comment? That's kinda weird. Following the examples of the  
above, surely a trapping NaN should be -1e+-0. Ugh. Of course,  
outputting a comment after every NaN does help with the "what the  
hell is this" problem.

James