inexact->exact

[Jim White]

Marco Vezzoli wrote:
> jim@pagesmiths.com wrote:
> 
>>>...
>>>call to log (0.0)
>>>return from log => #i-1/0
>>
>>That is the correct result.  The logarithm of zero is not a number. 
> 
> You are right, I simply copied the routine and the examples the author
> gived which included tests with zeroes. Maybe the scheme implementations
> where the routine was written are more permissive (or simply wrong) with
> the log arguments.

As far as a the specification goes, since the result of (log 0) is not 
defined, there isn't any way to be wrong.  Other implementations are 
probably doing what Java does, which is to return a negative infinity 
float.  So actually I should have said it is undefined for Scheme (and 
CL) specifications because IEEE does define -infinity as a number.

Same goes for inexact->exact's use of an exception for an invalid 
number.  Friendlier though would be to return infinity (negative or 
positive depending on the numerator's sign) rather than an exception at 
that point.

Jim