[Bug libfortran/93871] COTAN is slow for complex types

[thenlich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93871

--- Comment #21 from Thomas Henlich <thenlich at gcc dot gnu.org> ---
One should also ask: What is the least surprising way to implement the
cotangent function?

If someone uses a (non-standard) function bearing a name similar to "tangent",
they probably expect a function similar in precision and runtime to the
standard tangent function, and nothing which is more accurate in certain
ranges, but which is also slower.

For being able to use a construct like "y = a * cotan(x)" instead of "y = a /
tan(x)" there should be no additional punishment aside from standard
non-compliance.