Re: (atan 0 x) with gauche 0.9.14

R7RS has a pretty comprehensive table of all corner cases, but (atan 0 0)
is said to be undefined (when both arguments are exact zeros).  I decided
to return NaN to prevent people from accidentally relying on any specific
value.






On Wed, Apr 17, 2024 at 9:23 PM Jens Thiele <[email protected]> wrote:

> Shiro Kawai <[email protected]> writes:
>
> > Fix pushed.  Also realized that (atan 0.0 0) and (atan -0.0 0) need a
> > special treatment (the second arg is exact).
>
> Thanks!
>
> Total: 39739 tests, 39739 passed,     0 failed,     0 aborted.
>
> gosh$ (gauche-version)
> "0.9.14-p1"
> gosh$ (radians->degrees (atan 0 -1))
> 180.0
>
> Greetings
> Jens
>
> PS: at the moment I don't really want to follow into the (atan ±0 ±0)
> rabbit hole but:
>
> gosh$ (atan 0 0)
> +nan.0
>
> scheme@(guile-user)> (atan 0 0)
> $16 = 0.0
>
> emacs
> (atan 0 0)
> 0.0
>
> sbcl
> * (atan 0 0)
> 0.0
>
> chicken
> #;1> (atan 0 0)
> 0.0
>
> C
> atan2(0,0)
> 0.0
>
> maxima:
> (%i1) atan2(0,0);
>
> atan2: atan2(0,0) is undefined.
>
>
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