From a42ab98fcbdb42df6dd5e91379a7c623fbd1525c Mon Sep 17 00:00:00 2001
From: Sam Buercklin <sam.buercklin@gmail.com>
Date: Sun, 24 Jul 2022 15:32:59 -0400
Subject: [PATCH 1/5] ustrip, trig rules for degrees

---
 src/UnitfulChainRules.jl |  9 +++++++--
 src/extras.jl            | 13 +++++++++++++
 src/trig.jl              | 17 +++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 src/extras.jl
 create mode 100644 src/trig.jl

diff --git a/src/UnitfulChainRules.jl b/src/UnitfulChainRules.jl
index a82ffd8..db52c4c 100644
--- a/src/UnitfulChainRules.jl
+++ b/src/UnitfulChainRules.jl
@@ -1,12 +1,17 @@
 module UnitfulChainRules
 
 using Unitful
-using Unitful: Quantity, Units
-using ChainRulesCore: NoTangent
+using Unitful: Quantity, Units, NoDims
+using ChainRulesCore: NoTangent, @scalar_rule
 import ChainRulesCore: rrule, frule, ProjectTo
 
 include("./rrules.jl")
 include("./frules.jl")
 include("./projection.jl")
 
+
+include("./extras.jl") # Unitful-specific rules
+
+include("./trig.jl") # sin, cos, tan, etc for degrees
+
 end # module
diff --git a/src/extras.jl b/src/extras.jl
new file mode 100644
index 0000000..f2b122d
--- /dev/null
+++ b/src/extras.jl
@@ -0,0 +1,13 @@
+# Identity operation for non-Quantities
+rrule(::typeof(ustrip), x::Number) = x, (Δ) -> (NoTangent(), Δ * one(x))
+
+# Divide by the stripped units to backprop
+function rrule(::typeof(ustrip), x::Quantity{T,D,U}) where {T,D,U}
+    ustripped = ustrip(x)
+    project_x = ProjectTo(x)
+    invU = inv(U())
+
+    ustrip_pb(Δ) = (NoTangent(), project_x(Δ * invU))
+
+    return ustripped, ustrip_pb
+end
diff --git a/src/trig.jl b/src/trig.jl
new file mode 100644
index 0000000..f7088e3
--- /dev/null
+++ b/src/trig.jl
@@ -0,0 +1,17 @@
+###########################
+#=
+    Trigonometric Rules for Degrees
+
+    Let dx be differential in radians/dimensionless, dx° be in degrees
+    df/dx° = df/dx * dx/dx° = df/dx * π/180°
+=#
+###########################
+const DEGREE_QUANTITY = Quantity{<:Number,NoDims,typeof(u"°")}
+const TO_RAD = π/180u"°"
+
+@scalar_rule sin(x::DEGREE_QUANTITY) cos(x) * TO_RAD
+@scalar_rule cos(x::DEGREE_QUANTITY) -sin(x) * TO_RAD
+@scalar_rule tan(x::DEGREE_QUANTITY) (1 + Ω^2) * TO_RAD
+@scalar_rule csc(x::DEGREE_QUANTITY) -Ω * cot(x) * TO_RAD
+@scalar_rule sec(x::DEGREE_QUANTITY) Ω * tan(x) * TO_RAD
+@scalar_rule cot(x::DEGREE_QUANTITY) -(1 + Ω^2) * TO_RAD

From 80e2327556c9eeab9b9ffc8fffa595dbb97f9803 Mon Sep 17 00:00:00 2001
From: Sam Buercklin <sam.buercklin@gmail.com>
Date: Sun, 24 Jul 2022 16:47:09 -0400
Subject: [PATCH 2/5] Restructure + add tests

---
 Project.toml                     |  3 +-
 test/extras.jl                   | 11 ++++
 test/rrules-frules-projection.jl | 85 ++++++++++++++++++++++++++++++
 test/runtests.jl                 | 89 +++-----------------------------
 test/trig.jl                     | 30 +++++++++++
 5 files changed, 136 insertions(+), 82 deletions(-)
 create mode 100644 test/extras.jl
 create mode 100644 test/rrules-frules-projection.jl
 create mode 100644 test/trig.jl

diff --git a/Project.toml b/Project.toml
index 69dab36..03287dc 100644
--- a/Project.toml
+++ b/Project.toml
@@ -14,7 +14,8 @@ julia = "1"
 
 [extras]
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "Random"]
+test = ["Test", "Random", "SafeTestsets"]
diff --git a/test/extras.jl b/test/extras.jl
new file mode 100644
index 0000000..d8d3f06
--- /dev/null
+++ b/test/extras.jl
@@ -0,0 +1,11 @@
+using Unitful
+using UnitfulChainRules
+using ChainRulesCore
+
+@testset "ustrip" begin
+	x = 5.0u"m"
+	Ω, pb = rrule(ustrip, x)
+
+	@test Ω == 5.0
+	@test last(pb(2.0)) == 2.0/u"m"
+end
\ No newline at end of file
diff --git a/test/rrules-frules-projection.jl b/test/rrules-frules-projection.jl
new file mode 100644
index 0000000..0f0c33a
--- /dev/null
+++ b/test/rrules-frules-projection.jl
@@ -0,0 +1,85 @@
+using Unitful
+using UnitfulChainRules
+
+using ChainRulesCore: frule, rrule, ProjectTo, NoTangent
+
+using Random
+rng = VERSION >= v"1.7" ? Random.Xoshiro(0x0451) : Random.MersenneTwister(0x0451)
+
+@testset "ProjectTo" begin
+    real_test(proj, val) = proj(val) == real(val)
+    complex_test(proj, val) = proj(val) == val
+    ru = randn(rng)
+    ruval = ru*u"W"
+    p_ruval = ProjectTo(ruval)
+
+    cu = randn(rng, ComplexF64)
+    cuval = cu*u"kg"
+    p_cuval = ProjectTo(cuval)
+
+    p_real = ProjectTo(ru)
+    p_complex = ProjectTo(cu)
+
+    δr = randn(rng)
+    δrval = δr*u"m"
+
+    δc = randn(rng, ComplexF64)
+    δcval = δc*u"L"
+
+    # Test projection onto real unitful quantities
+    for δ in (δrval, δcval, ru, cu)
+        @test real_test(p_ruval, δ)
+    end
+
+    # Test projection onto complex unitful quantities
+    for δ in (δrval, δcval, ru, cu)
+        @test complex_test(p_cuval, δ)
+    end 
+
+    # Projecting Unitful quantities onto real values
+    @test p_real(δrval) == δrval
+    @test p_real(δcval) == real(δcval)
+
+    # Projecting Unitful quantities onto complex values
+    @test p_complex(δrval) == δrval
+    @test p_complex(δcval) == δcval
+end
+
+@testset "rrules" begin
+    @testset "Quantity rrule" begin
+        UT = typeof(1.0*u"W")
+        x = randn(rng)
+        δx = randn(rng)
+        Ω, pb = rrule(UT, x)
+        @test Ω == x * u"W"
+        @test pb(δx) == (NoTangent(), δx * u"W")
+    end
+    @testset "* rrule" begin
+        x = randn(rng)*u"W" 
+        y = u"m"
+        z = u"L"
+        Ω, pb = rrule(*, x, y, z)
+        @test Ω == x*y*z
+        δ = randn(rng)
+        @test pb(δ) == (NoTangent(), δ*y*z, NoTangent(), NoTangent())
+    end
+end
+
+@testset "frules" begin
+    @testset "Quantity frule" begin
+        UT = typeof(1.0*u"W")
+        x = randn(rng)
+        δx = randn(rng)
+        X, ∂X = frule((nothing, δx), UT, x)
+        @test X == x * u"W"
+        @test ∂X == δx * u"W"
+    end
+    @testset "* frule" begin
+        x = randn(rng)*u"W" 
+        δx = randn(rng)*u"L"
+        y = u"m"
+        X, ∂X = frule((nothing, δx, nothing), *, x, y)
+        @test X == x*y
+        @test ∂X == δx*y
+    end
+end
\ No newline at end of file
diff --git a/test/runtests.jl b/test/runtests.jl
index 88d16f9..39ec9aa 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,88 +1,15 @@
-using Unitful
-using UnitfulChainRules
-
-using ChainRulesCore: frule, rrule, ProjectTo, NoTangent
-
-using Random
+using SafeTestsets
 
 using Test
 
-rng = VERSION >= v"1.7" ? Random.Xoshiro(0x0451) : Random.MersenneTwister(0x0451)
-
-@testset "ProjectTo" begin
-    real_test(proj, val) = proj(val) == real(val)
-    complex_test(proj, val) = proj(val) == val
-    ru = randn(rng)
-    ruval = ru*u"W"
-    p_ruval = ProjectTo(ruval)
-
-    cu = randn(rng, ComplexF64)
-    cuval = cu*u"kg"
-    p_cuval = ProjectTo(cuval)
-
-    p_real = ProjectTo(ru)
-    p_complex = ProjectTo(cu)
-
-    δr = randn(rng)
-    δrval = δr*u"m"
-
-    δc = randn(rng, ComplexF64)
-    δcval = δc*u"L"
-
-    # Test projection onto real unitful quantities
-    for δ in (δrval, δcval, ru, cu)
-        @test real_test(p_ruval, δ)
-    end
-
-    # Test projection onto complex unitful quantities
-    for δ in (δrval, δcval, ru, cu)
-        @test complex_test(p_cuval, δ)
-    end 
-
-    # Projecting Unitful quantities onto real values
-    @test p_real(δrval) == δrval
-    @test p_real(δcval) == real(δcval)
-
-    # Projecting Unitful quantities onto complex values
-    @test p_complex(δrval) == δrval
-    @test p_complex(δcval) == δcval
+@safetestset "rrules, frules, ProjectTo" begin
+    include("./rrules-frules-projection.jl")
 end
 
-@testset "rrules" begin
-    @testset "Quantity rrule" begin
-        UT = typeof(1.0*u"W")
-        x = randn(rng)
-        δx = randn(rng)
-        Ω, pb = rrule(UT, x)
-        @test Ω == x * u"W"
-        @test pb(δx) == (NoTangent(), δx * u"W")
-    end
-    @testset "* rrule" begin
-        x = randn(rng)*u"W" 
-        y = u"m"
-        z = u"L"
-        Ω, pb = rrule(*, x, y, z)
-        @test Ω == x*y*z
-        δ = randn(rng)
-        @test pb(δ) == (NoTangent(), δ*y*z, NoTangent(), NoTangent())
-    end
+@safetestset "Trig Operations" begin
+    include("./trig.jl")
 end
 
-@testset "frules" begin
-    @testset "Quantity frule" begin
-        UT = typeof(1.0*u"W")
-        x = randn(rng)
-        δx = randn(rng)
-        X, ∂X = frule((nothing, δx), UT, x)
-        @test X == x * u"W"
-        @test ∂X == δx * u"W"
-    end
-    @testset "* frule" begin
-        x = randn(rng)*u"W" 
-        δx = randn(rng)*u"L"
-        y = u"m"
-        X, ∂X = frule((nothing, δx, nothing), *, x, y)
-        @test X == x*y
-        @test ∂X == δx*y
-    end
-end
\ No newline at end of file
+@safetestset "Extras" begin
+    include("./extras.jl")
+end
diff --git a/test/trig.jl b/test/trig.jl
new file mode 100644
index 0000000..1b5f19a
--- /dev/null
+++ b/test/trig.jl
@@ -0,0 +1,30 @@
+using Unitful
+using UnitfulChainRules
+
+using ChainRulesCore
+
+using Random
+rng = VERSION >= v"1.7" ? Random.Xoshiro(0x0451) : Random.MersenneTwister(0x0451)
+
+dsin(Ω, x) = cos(x)
+dcos(Ω, x) = -sin(x)
+dtan(Ω, x) = 1 + Ω^2
+dcsc(Ω, x) = - Ω * cot(x)
+dsec(Ω, x) = Ω * tan(x)
+dcot(Ω, x) = -(1 + Ω^2)
+
+for (f, df) in (
+	(:sin, :dsin), (:cos,:dcos), (:tan,:dtan), (:csc,:dcsc), (:sec,:dsec), (:cot,:dcot)
+	)
+	eval(
+		quote
+			@testset "$($f)" begin
+				x = rand(rng)u"°"
+
+				Ω, pb = rrule($f, x)
+				@test Ω == $f(x)
+				@test last(pb(1.0)) ≈ $df(Ω, x) * π/180u"°"
+			end
+		end
+	)
+end
\ No newline at end of file

From 18d5597d517eded3aecd4af009be0d00e0dd0b9f Mon Sep 17 00:00:00 2001
From: Sam Buercklin <sam@metalenz.com>
Date: Thu, 28 Jul 2022 09:54:00 -0400
Subject: [PATCH 3/5] uconvert rrule

---
 src/UnitfulChainRules.jl |  2 +-
 src/extras.jl            | 12 ++++++++++++
 test/extras.jl           |  8 ++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/UnitfulChainRules.jl b/src/UnitfulChainRules.jl
index db52c4c..ebf442e 100644
--- a/src/UnitfulChainRules.jl
+++ b/src/UnitfulChainRules.jl
@@ -1,7 +1,7 @@
 module UnitfulChainRules
 
 using Unitful
-using Unitful: Quantity, Units, NoDims
+using Unitful: Quantity, Units, NoDims, FreeUnits
 using ChainRulesCore: NoTangent, @scalar_rule
 import ChainRulesCore: rrule, frule, ProjectTo
 
diff --git a/src/extras.jl b/src/extras.jl
index f2b122d..e590576 100644
--- a/src/extras.jl
+++ b/src/extras.jl
@@ -11,3 +11,15 @@ function rrule(::typeof(ustrip), x::Quantity{T,D,U}) where {T,D,U}
 
     return ustripped, ustrip_pb
 end
+
+function rrule(::typeof(uconvert), u::FreeUnits{N,D,A}, x::TX) where {N,D,A,TX}
+    x_convert = uconvert(u, x)
+    conversion = uconvert(u, oneunit(x)) / oneunit(x)
+    project_x = ProjectTo(x)
+
+    function uconvert_pb(Δ)
+        return (NoTangent(), NoTangent(), project_x(Δ * conversion))
+    end
+    
+    return x_convert, uconvert_pb
+end
\ No newline at end of file
diff --git a/test/extras.jl b/test/extras.jl
index d8d3f06..64f4692 100644
--- a/test/extras.jl
+++ b/test/extras.jl
@@ -8,4 +8,12 @@ using ChainRulesCore
 
 	@test Ω == 5.0
 	@test last(pb(2.0)) == 2.0/u"m"
+end
+
+@testset "uconvert" begin
+	x = 30.0u"°"
+	Ω, pb = rrule(uconvert, u"rad", x)
+
+	@test Ω ≈ (π/6)u"rad"
+	@test last(pb(1.0)) ≈ π*u"rad"/180u"°"
 end
\ No newline at end of file

From c88449bad007c46a19578e5a1fa3b0afb1f96974 Mon Sep 17 00:00:00 2001
From: Sam Buercklin <sam@metalenz.com>
Date: Thu, 28 Jul 2022 10:05:15 -0400
Subject: [PATCH 4/5] abs rrule

---
 src/UnitfulChainRules.jl |  6 +++++-
 src/math.jl              |  8 ++++++++
 test/math.jl             | 12 ++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 src/math.jl
 create mode 100644 test/math.jl

diff --git a/src/UnitfulChainRules.jl b/src/UnitfulChainRules.jl
index ebf442e..11a7430 100644
--- a/src/UnitfulChainRules.jl
+++ b/src/UnitfulChainRules.jl
@@ -5,13 +5,17 @@ using Unitful: Quantity, Units, NoDims, FreeUnits
 using ChainRulesCore: NoTangent, @scalar_rule
 import ChainRulesCore: rrule, frule, ProjectTo
 
+const REALCOMPLEX = Union{Real, Complex}
+
 include("./rrules.jl")
 include("./frules.jl")
 include("./projection.jl")
 
 
-include("./extras.jl") # Unitful-specific rules
+include("./extras.jl") # extra Unitful-specific rules
 
 include("./trig.jl") # sin, cos, tan, etc for degrees
 
+include("./math.jl") # other math 
+
 end # module
diff --git a/src/math.jl b/src/math.jl
new file mode 100644
index 0000000..e419b60
--- /dev/null
+++ b/src/math.jl
@@ -0,0 +1,8 @@
+function rrule(::typeof(abs), x::Unitful.Quantity{T,D,U}) where {T<:REALCOMPLEX, D, U}
+    Ω = abs(x)
+    function abs_pullback(ΔΩ)
+        signx = isreal(x) ? sign(x) : x / ifelse(iszero(x), oneunit(Ω), Ω)
+        return (NoTangent(), signx * real(ΔΩ))
+    end
+    return Ω, abs_pullback
+end
\ No newline at end of file
diff --git a/test/math.jl b/test/math.jl
new file mode 100644
index 0000000..9d44998
--- /dev/null
+++ b/test/math.jl
@@ -0,0 +1,12 @@
+using Unitful
+using UnitfulChainRules
+
+using ChainRulesCore
+
+@testset "abs" begin
+    z = (1 + im)u"W"
+    Ω, pb = rrule(abs, z)
+
+    @test Ω ≈ sqrt(2)u"W"
+    @test last(pb(1.0)) ≈ (1 + im)/sqrt(2)
+end
\ No newline at end of file

From ce64dfb501a2176ededd55dd89d46cd8373837d6 Mon Sep 17 00:00:00 2001
From: Sam Buercklin <sam@metalenz.com>
Date: Thu, 28 Jul 2022 10:10:26 -0400
Subject: [PATCH 5/5] version bump

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 03287dc..c704f40 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "UnitfulChainRules"
 uuid = "f31437dd-25a7-4345-875f-756556e6935d"
 authors = ["Sam Buercklin <sam.buercklin@gmail.com>"]
-version = "0.1.0"
+version = "0.1.1"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"