Figured out complicated parametric subtyping of functors, functions, …

…and their types

scripts/prototype.jl

@@ -1,14 +1,27 @@
-density_profile(::Val{:one}, x::Real; a::Real)::Float64 = x + a
+struct DensityProfileFunctionType{MediumSymbol} <: Function end
 
-struct DensityProfile{F <: Function}
-    profile::F
+const ocean_density_profile = DensityProfileFunctionType{:Ocean}()
 
-    function DensityProfile(model::Val; pars...)
-        profile(x::Real)::Float64 = density_profile(model, x; pars...)
-        new{typeof(profile)}(profile)
+ocean_density_profile(::Val{:Homogeneous}, z::Real; ρ::Real = 1500.0) = ρ
+
+const seabed_density_profile = DensityProfileFunctionType{:Seabed}()
+
+seabed_density_profile(::Val{:Homogeneous}, z::Real; ρ::Real = 3000.0) = ρ
+
+abstract type OceanographyProfile <: Function end
+
+struct DensityProfile{MediumSymbol, ProfileFunctionType <: Function} <: OceanographyProfile
+    profile::ProfileFunctionType
+
+    function DensityProfile{MediumSymbol}(model::Val; pars...) where {MediumSymbol}
+        profile(z::Real) = ocean_density_profile(model, z; pars...)
+        return new{MediumSymbol, profile |> typeof}(profile)
     end
 end
 
-function (den::DensityProfile{F} where {F <: Function})(x::Real)
-    den.profile(x)::Float64
+function (den::DensityProfile{MediumSymbol, ProfileFunctionType} where {MediumSymbol, ProfileFunctionType})(z::Real)
+    den.profile(z)
 end
+
+ocn_den = DensityProfile{:Ocean}(Val(:Homogeneous); ρ = 1520.0)
+sbd_den = DensityProfile{:Seabed}(Val(:Homogeneous); ρ = 3200.0)