From 0f19eaf6e11a7bac704563960c1fe1423ebaa8cf Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 29 Jan 2015 15:38:53 +1100
Subject: [PATCH] comments

---
 polynomial.cpp | 3 +++
 polynomial.hpp | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/polynomial.cpp b/polynomial.cpp
index 194a5f0b..dc761a91 100644
--- a/polynomial.cpp
+++ b/polynomial.cpp
@@ -79,6 +79,9 @@ namespace util { namespace polynomial {
         const float _c = coeffs[2];
         const float _d = coeffs[3];
 
+        // Take care of degenerate quadratic cases. We can also pass off if 'd'
+        // is zero, but the benefit isn't clear given we have to merge results
+        // at the end anyway.
         if (almost_zero (_a)) {
             auto s = solve<2> ({_b, _c, _d});
             return {s[0], s[1], std::numeric_limits<float>::quiet_NaN () };
diff --git a/polynomial.hpp b/polynomial.hpp
index 29f61cdc..b7490178 100644
--- a/polynomial.hpp
+++ b/polynomial.hpp
@@ -25,6 +25,9 @@
 
 namespace util {
     namespace polynomial {
+        // Invalid solutions are represented by NaN. They are guaranteed to
+        // be at the end of the solution list, so they are safe to skip on the
+        // first instance.
         template <size_t S>
         std::array<float,S>
         solve (std::array<float,S+1>);