From 56641d5838cba59fa55d82af2e0d495185b227cc Mon Sep 17 00:00:00 2001
From: Matt Huszagh <huszaghmatt@gmail.com>
Date: Thu, 17 Dec 2020 10:02:35 -0800
Subject: [PATCH] atan2: specify why we cannot use more than 15 bits for the
 atan argument

---
 dsp/src/trig.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/dsp/src/trig.rs b/dsp/src/trig.rs
index 53aecfa..6d0acff 100644
--- a/dsp/src/trig.rs
+++ b/dsp/src/trig.rs
@@ -57,7 +57,9 @@ pub fn atan2(y: i32, x: i32) -> i32 {
     // We need to share the 31 available non-sign bits between the
     // atan argument and constant factors used in the atan
     // approximation. Sharing the bits roughly equally between them
-    // gives good accuracy.
+    // gives good accuracy. Additionally, we cannot increase the
+    // number of atan argument bits beyond 15 because we must square
+    // it.
     const ATAN_ARGUMENT_BITS: usize = 15;
     let ratio = (min << ATAN_ARGUMENT_BITS) / max;