Is there a way to have a nested expression loop

New to Julia
1

I’m trying to unwrap a vector of vectors of vectors into one vector and my first thought is to

[k for i in vecs, j in i, k in j]
or 
[k for k in j, j in i, i in vecs]

ERROR: UndefVarError: i/j not defined

Do I need to use a full for loop or am I missing something?

2

Perhaps you mean something like:

[ k for i in vecs for j in 1:i for k in 1:j ]

Your i in j in i is an element and not iterable. Same for j in k in j.

3

ok, I see vector of vector… ok, it should work, but with for and not , separated.

julia> a= [ [1,2,3], [2,3,4,5,6] ]
2-element Vector{Vector{Int64}}:
 [1, 2, 3]
 [2, 3, 4, 5, 6]

julia> [j for i in a for j in i ]
8-element Vector{Int64}:
 1
 2
 3
 2
 3
 4
 5
 6

Iterators.flatten(a) isn’t going deep, so it’s a bit tricky with that …

4

Best to check here: https://discourse.julialang.org/t/how-do-you-unfold-a-nested-julia-array

5

yes! there it is! thank you. easy enough to iterate with flatten.