--- a/src/DifferentiableFN.jl	Wed Dec 15 01:09:09 2021 +0200
+++ b/src/DifferentiableFN.jl	Wed Dec 22 11:13:38 2021 +0200
@@ -69,8 +69,8 @@
 
 # Squared norm of a differentiable function as a differentiable function
 
-ℝ = Float64
-ℝⁿ = Vector{Float64}
+const ℝ = Float64
+const ℝⁿ = Vector{Float64}
 
 struct Squared <: DiffF{ℝⁿ, ℝ, MatrixOp{ℝ}}
     r :: DiffF{ℝⁿ, ℝⁿ, MatrixOp{ℝ}}