From 14488ddd92df383982f67120c186baaf74ceace9 Mon Sep 17 00:00:00 2001
From: Sei Lisa <sei-lisa@email.fake>
Date: Thu, 22 Dec 2016 01:08:07 +0100
Subject: [PATCH] Improve behaviour of llAtan2 to make it closer to SL's.

Especially regarding NaN inputs. Add regression tests.
---
 lslopt/lslbasefuncs.py |  8 ++++++++
 testfuncs.py           | 24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lslopt/lslbasefuncs.py b/lslopt/lslbasefuncs.py
index 87cb3c7..459be81 100644
--- a/lslopt/lslbasefuncs.py
+++ b/lslopt/lslbasefuncs.py
@@ -835,6 +835,14 @@ def llAsin(f):
 def llAtan2(y, x):
     assert isfloat(y)
     assert isfloat(x)
+    if math.isnan(x) and math.isnan(y):
+        if math.copysign(1, x) == -1 and math.copysign(1, y) == -1:
+            return -NaN
+        return NaN
+    elif math.isnan(x):
+        return x
+    elif math.isnan(y):
+        return y
     return F32(math.atan2(y, x))
 
 def llAxes2Rot(fwd, left, up):
diff --git a/testfuncs.py b/testfuncs.py
index 63d1c3c..441b907 100644
--- a/testfuncs.py
+++ b/testfuncs.py
@@ -880,6 +880,30 @@ def do_tests():
     test('llAsin(2.0)', NaN)
     test('llAcos(2.0)', NaN)
     test('llAtan2(0.0, 0.0)', 0.0)
+    test('llAtan2(-0.0, -1.0)', F32(-math.pi))
+    test('llAtan2(0.0, -1.0)', F32(math.pi))
+    test('llAtan2(-Infinity, -1.0)', F32(-math.pi/2))
+    test('llAtan2(Infinity, -1.0)', F32(math.pi/2))
+    test('llAtan2(NaN, -1.0)', NaN)
+    test('llAtan2(NaN, -0.0)', NaN)
+    test('llAtan2(NaN,  0.0)', NaN)
+    test('llAtan2(NaN,  1.0)', NaN)
+    test('llAtan2(-NaN, -1.0)', -NaN)
+    test('llAtan2(-NaN, -0.0)', -NaN)
+    test('llAtan2(-NaN,  0.0)', -NaN)
+    test('llAtan2(-NaN,  1.0)', -NaN)
+    test('llAtan2(-1.0, NaN)', NaN)
+    test('llAtan2(-0.0, NaN)', NaN)
+    test('llAtan2( 0.0, NaN)', NaN)
+    test('llAtan2( 1.0, NaN)', NaN)
+    test('llAtan2(-1.0, -NaN)', -NaN)
+    test('llAtan2(-0.0, -NaN)', -NaN)
+    test('llAtan2( 0.0, -NaN)', -NaN)
+    test('llAtan2( 1.0, -NaN)', -NaN)
+    test('llAtan2(-NaN, -NaN)', -NaN)
+    test('llAtan2(-NaN, NaN)', NaN)
+    test('llAtan2(NaN, -NaN)', NaN)
+    test('llAtan2(NaN, NaN)', NaN)
 
     # nan and -nan in llList2CSV
     test('llList2CSV([llSin(F32(4e38))])', u'-nan')