Preferred type expression for a vector of vectors

New to Julia
10

Looked at the topic, and made a julia0.7-rc2 version below, using your suggestion in the topic. It worked without error/warnings :slight_smile:

julia> bc(f) = (args...) -> f.(args...)
bc (generic function with 1 method)

julia> f(u::AbstractVector{<:AbstractVector{<:Real}}) = (bc(+)).(u, 1)
f (generic function with 1 method)

julia> x = Vector{Vector{T} where T<:Real}(undef,2)
2-element Array{Array{T,1} where T<:Real,1}:
 #undef
 #undef

julia> x[1] = [1,2]; x[2] = [3,4];

julia> f(x)
2-element Array{Array{Int64,1},1}:
 [2, 3]
 [4, 5]

julia> y = Vector{Vector{Int64}}(undef,2)
2-element Array{Array{Int64,1},1}:
 #undef
 #undef

julia> y[1] = [5,6]; y[2] = [7,8];

julia> f(y)
2-element Array{Array{Int64,1},1}:
 [6, 7]
 [8, 9]

julia>