[FR] Transform which maps a tuple onto a user-provided struct

src/aggregation.jl

@@ -482,3 +482,33 @@ function _domain_label(t::TransformTuple, index::Int)
     end
     error("internal error")
 end
+
+####
+#### type wrapper transformation
+####
+
+struct TypeWrapperTransformation{T} <: AbstractTransform
+    inner_transformation::AbstractTransform
+end
+
+function as(::Type{T}, transformation) where T
+    TypeWrapperTransformation{T}(transformation)
+end
+
+dimension(t::TypeWrapperTransformation) = dimension(t.inner_transformation)
+
+function transform(t::TypeWrapperTransformation{T}, x) where T
+    T(transform(t.inner_transformation, x)...)
+end
+# function transform(t::TypeWrapperTransformation{T}, x::VectorTransform) where T
+#     T(x...)
+# end
+# function transform(t::TypeWrapperTransformation{T}, x::ScalarTransform) where T
+#     T(x)
+# end
+function inverse(t::TypeWrapperTransformation{T}, x::T) where T
+    fields = [getfield(x, i) for i in 1:nfields(x)]
+    inverse(t.inner_transformation, fields)
+end
+
+

test/runtests.jl

@@ -541,6 +541,25 @@ end
 
 end
 
+@testset "transform to custom type" begin
+    struct CustomType
+        a::Float64
+        b::Float64
+    end
+
+    t1 = as((a = asℝ, b = asℝ))
+    t2 = as(CustomType, t1)
+    y = transform(t2, [1.0, 2.0])
+    @test y == CustomType(1.0, 2.0)
+    @test inverse(t2, y) == [1.0, 2.0]
+
+    t3 = as(Vector, asℝ₊, 2)
+    t4 = as(CustomType, t3)
+    y = transform(t4, [0.0, 0.0])
+    @test y == CustomType(1.0, 1.0)
+    @test inverse(t4, y) == [0.0, 0.0]
+end
+
 ####
 #### log density correctness checks
 ####