Reduce AffineMap application to Linear and Translation

Author: jw3126

REQUIRE

@@ -1,4 +1,4 @@
-julia 0.6
+julia 0.7
 StaticArrays
 Rotations 0.3.0
 Compat 0.69

src/affine.jl

@@ -100,8 +100,10 @@ struct AffineMap{M, V} <: AbstractAffineMap
     translation::V
 end
 
-function (trans::AffineMap{M, V})(x) where {M, V}
-    trans.linear * x + trans.translation
+function (trans::AffineMap)(x)
+    l = LinearMap(trans.linear)
+    t = Translation(trans.translation)
+    t(l(x))
 end
 
 # Note: the expression `Tx - dT*Tx` will have large cancellation error for

test/affine.jl

@@ -4,6 +4,18 @@ struct SquareMe <: Transformation; end
 (::SquareMe)(x) = x.^2
 CoordinateTransformations.transform_deriv(::SquareMe, x0) = Matrix(Diagonal(2*x0))
 
+struct Ray37
+    origin::Vector
+    direction::Vector
+end
+function (m::LinearMap)(r::Ray37)
+    Ray37(m(r.origin),
+          m(r.direction))
+end
+function (t::Translation)(r::Ray37)
+    Ray37(t(r.origin),
+          r.direction)
+end
 
 @testset "Common Transformations" begin
     @testset "AffineMap" begin
@@ -97,6 +109,18 @@ CoordinateTransformations.transform_deriv(::SquareMe, x0) = Matrix(Diagonal(2*x0
         end
     end
 
+    @testset "application of AffineMap in terms of LinearMap and Translation" begin
+        origin = randn(3)
+        direction = randn(3)
+        linear = randn(3,3)
+        trans = randn(3)
+        r = Ray37(origin, direction)
+        expected = Ray37(linear*origin+trans, linear*direction)
+        result   = AffineMap(linear, trans)(r)
+        @test expected.origin ≈ result.origin
+        @test expected.direction ≈ result.direction
+    end
+
 #=
     @testset "Rotation2D on Polar" begin
         p = Polar(2.0, 1.0)