I find Parameters.jl and its function reconstruct() a very convenient way to handle models that need to be computed under many set of parameters. The feature that one can define a default value for a parameter that is a function of other parameters is really useful. However, consider the following:

using Parameters
@with_kw struct Para
a::Float64
b = a + 1
end
p = Para(a=1)

Which returns a struct with a = 1 and b = 2. Now if one uses reconstruct:

p2 = reconstruct(p,a=5)

I would like p2 to return a struct with a = 5 and b = 6, however it returns a struct with a = 5 and b = 2 (b is not updated to the new value of a). In my opinion, for most applications it would make much more sense that reconstruct makes b still consistent with the parameter a. Does anyone know any other option to achieve the desired result (in as simple and parsimonious way)?

For extensive sets of parameters with precomputed quantities, I usually try to organize my code like this:

struct Parameters{...}
...
end
struct PrecomputedModel{TP <: Parameters, ...}
parameters::TP
...
end
function PrecomputedModel(parameters::Parameters)
... # do the precalculations
end

Then the two sets of quantities are organized separately, which I find leads to cleaner code.