From 152ce4a164a4602bf8804090e79b1ca59772f70c Mon Sep 17 00:00:00 2001
From: Mike J Innes <mike.j.innes@gmail.com>
Date: Tue, 22 Jan 2019 10:07:42 +0000
Subject: [PATCH] conversions for dual numbers

---
 src/tracker/lib/real.jl | 6 ++++++
 test/tracker.jl         | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/src/tracker/lib/real.jl b/src/tracker/lib/real.jl
index b1fbb19fd8..a4f90a0c1d 100644
--- a/src/tracker/lib/real.jl
+++ b/src/tracker/lib/real.jl
@@ -99,6 +99,12 @@ import Base:^
 
 ^(a::TrackedReal, b::Integer) = track(^, a, b)
 
+# Hack for conversions
+
+using ForwardDiff: Dual
+
+(T::Type{<:Real})(x::Dual) = Dual(T(x.value), map(T, x.partials.values))
+
 # Tuples
 
 struct TrackedTuple{T<:Tuple}
diff --git a/test/tracker.jl b/test/tracker.jl
index 6b35f9cfc2..4380402e80 100644
--- a/test/tracker.jl
+++ b/test/tracker.jl
@@ -189,6 +189,8 @@ end
 @test gradtest(x -> meanpool(x, (2,2)), rand(10, 10, 3, 2))
 @test gradtest(x -> meanpool(x, (2,2,2)), rand(5, 5, 5, 3, 2))
 
+@test gradtest(x -> Float64.(x), 5)
+
 @testset "equality & order" begin
     # TrackedReal
     @test param(2)^2 == param(4)