[gambit-list] Patch to correct treatment of exact 0
Marc Feeley
feeley at iro.umontreal.ca
Tue Sep 24 17:35:04 EDT 2013
Thanks for the patch.
Marc
On 2013-09-24, at 2:11 PM, Bradley Lucier <lucier at math.purdue.edu> wrote:
> Marc:
>
> The numerical library currently returns
>
>> (expt 0 1.)
> 0
>> (/ 0 1.)
> 0
>> (/ 0 1.+1.i)
> 0
>
> This small patch has it return
>
>> (expt 0 1.)
> 0.
>> (/ 0 1.)
> 0.
>> (/ 0 1.+1.i)
> 0.+0.i
>
> which is what I believe R6RS does.
>
> Gambit now passes most of the arithmetic and trigonometric and
> transcendental function tests in the "Test Programs" part of
>
> http://www.cesura17.net/~will/Professional/Standards/Scheme/R6RS/
>
> The remaining differences are accuracy issues. I'll need to recode the
> complex inverse hyperbolic and inverse trigonometric routines as in
> Kahan, W. "Branch Cuts for Complex Elementary Functions, or Much Ado
> About Nothing's Sign Bit".
>
> Brad
> <exact-zero.patch>
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