How do I declare an array of a derived type? (Julia)

user_11664763 0
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I have a derived type represented by:

struct BoundaryCondition
  domain::MeshStructure
  left::BorderValue
  right::BorderValue
  bottom::BorderValue
  top::BorderValue
  back::BorderValue
  front::BorderValue
end

I want to create an array of this derived type, of size n_comp, which I have in my code as:

bc = Array{BoundaryCondition}(n_comp)
for i in 1:n_comp
  bc[i] = createBC(m)
  bc[i].left.a[:] = 0.0
  bc[i].left.b[:] = 1.0
  bc[i].left.c[:] = c_left[i]
end

But I receive an error:

ERROR: LoadError: MethodError: no method matching (Array{BoundaryCondition, N} where N)(::Int64)

What is the correct way to declare my array of type BoundaryCondition?

julia
1 Answers

If you want to preallocate it, you need to fill your array with something. For example, you can use undef (replace the Bool type and size with those of your problem):

julia> Vector{Bool}(undef, 3)
3-element Vector{Bool}:
 1
 0
 0

You can also use fill (same, replace false with your problem's default "fill" value):

julia> fill(false, 3)
3-element Vector{Bool}:
 0
 0
 0

If you don't need to preallocate, a good solution is comprehensions. Make a function of the index for creating your boundary condition, e.g.:

function my_BC(i)
    out = createBC(m)
    out.left.a[:] = 0.0
    out.left.b[:] = 1.0
    out.left.c[:] = c_left[i]
    return out
end

and then simply do

[my_BC(i) for i in 1:n_comp]
user_56021490
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