To: J3                                                     J3/18-276r1
From: Lorri Menard
Subject: IEEE pi trigonometric functions
Date: 2018-October-18

I  Introduction

At m217 J3 agreed to consider adding degree-argument versions of
some of the trigonometric intrinsic functions.

As part of the discussion it was suggested that we also add the
IEEE pi versions of the these same trigonometric intrinsic functions.


II  Use cases

This provides a portable mechanism for programs that need to use
the standard IEEE "pi" functions.   It will


III What I have in mind

Only generic functions are to be added for these names, with
behavior to match that listed in IEEE 754 latest.

(*) ACOSPI
     ACOSPI(x) returns acos(x)/pi in the domain of [-1,+1]
(*) ASINPI
     ASINPI(x) returns asin(x)/pi in the domain of [-1,+1]
 -  ATANPI
     ATANPI(x)  returns atan(x)/pi in the domain of (-inf,+inf)
 -  COSPI
     COSPI(x) returns cos(pi * x) in the domain of (-inf, +inf)
 -  SINPI
     SINPI(x) returns sin(pi * x) in the domain of (-inf, +inf)
(*) TANPI
     TANPI(x) returns tan(pi * x) in the domain of (-inf, +inf)
 -  ATAN2PI
     ATAN2PI(y,x) has a number of special rules, which should
     be handled as described in IEEE 754-201x

The intrinsics marked with "(*)" weren't found in the IEEE 754-2008
version of the document, but we are assured that these are being
added to the next release of IEEE 754.
Addendum:  Confirmed that these were found in the IEEE 754-201x
  draft document.