From 680ed234f190bc69d95b0c6319794954d32ba4a4 Mon Sep 17 00:00:00 2001
From: mhar100 <56600917+mhar100@users.noreply.github.com>
Date: Tue, 14 Jun 2022 14:09:31 -0400
Subject: [PATCH] added type for differentiate in chain_rules.jl

1. We should make sure that differentiate is being called on a polynomial p. (It is possible there are other meanings of differentiate for other types in the code.)
2. The function "pullback" is very generic, so I added some clarity.
---
 src/chain_rules.jl | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/chain_rules.jl b/src/chain_rules.jl
index fdeb75d8..2e3b9919 100644
--- a/src/chain_rules.jl
+++ b/src/chain_rules.jl
@@ -18,10 +18,10 @@ end
 function ChainRulesCore.frule((_, Δp, _), ::typeof(differentiate), p, x)
     return differentiate(p, x), differentiate(Δp, x)
 end
-function pullback(Δdpdx, x)
+function pullback_differentiate_polynomial(Δdpdx, x)
     return ChainRulesCore.NoTangent(), x * differentiate(x * Δdpdx, x), ChainRulesCore.NoTangent()
 end
-function ChainRulesCore.rrule(::typeof(differentiate), p, x)
+function ChainRulesCore.rrule(::typeof(differentiate), p::APL, x)
     dpdx = differentiate(p, x)
-    return dpdx, Base.Fix2(pullback, x)
+    return dpdx, Base.Fix2(pullback_differentiate_polynomial, x)
 end