define ArithmeticStyle for Dual

Author: KristofferC

src/dual.jl

@@ -20,6 +20,11 @@ struct Dual{T,V,N} <: Real
     end
 end
 
+##########
+# Traits #
+##########
+Base.ArithmeticStyle(::Type{<:Dual{T,V}}) where {T,V} = Base.ArithmeticStyle(V)
+
 ##############
 # Exceptions #
 ##############

test/GradientTest.jl

@@ -162,4 +162,11 @@ end
     @test_throws DimensionMismatch ForwardDiff.gradient(identity, fill(2pi, 10^6)) # chunk_mode_gradient
 end
 
+@testset "ArithmeticStyle" begin
+    function f(p)
+        sum(collect(0.0:p[1]:p[2]))
+    end
+    @test ForwardDiff.gradient(f, [0.2,25.0]) == [7875.0, 0.0]
+end
+
 end # module