PATCH -- Fix degree trignometric functions

[Fritz Reese]

On Sat, Mar 7, 2020 at 1:32 PM Steve Kargl
<sgk@troutmask.apl.washington.edu> wrote:
>
> Fix the simplification and handling of the degree trigonometric functions.
>  This includes fixing a number of ICEs.  See PR 93871.
>
>  ChangeLog and patch attached.

As the author of the original degree-trig functions I intend to review
this patch soon, and...

> On Fri, Mar 06, 2020 at 03:18:19PM -0800, Steve Kargl wrote:
> >
> >   3. Simplification routines do the following mappings:
> >      sind(x) = sin((pi/180) * x)     asind(x) = (180/pi) * asin(x)
> >      cosd(x) = cos((pi/180) * x)     acosd(x) = (180/pi) * acos(x)
> >      tand(x) = tan((pi/180) * x)     atand(x) = (180/pi) * atan(x)
> >      atan2d(y,x) = (180/pi) * atan2(y,x)
> >      cotand(x) = cotan((pi/180) * x)
> >      All computations are carried out by MPFR or MPC.
>
> In looking at some basic tests, the above simplification will
> need to be modified to do what ...
>
>
> >   5. New functions have been added to libgfortran to handle sind, cosd,
> >      and tand.
>
> ... these functions do.  Otherwise, things like cos(real(60+123*360))
> give wrong values.  Modifications are so easy even a lurker can do
> them.

... extend the patch to include these changes (unless someone
enthusiastic gets around to these mods before I do).

I should be able to start on this next week (around 16 March).

---
Fritz Reese