Nested list comprehensions in Julia

Question

In python I can do nested list comprehensions, for instance I can flatten the following array thus:

a = [[1,2,3],[4,5,6]]
[i for arr in a for i in arr]
         


        

Answer 1

This feature has been added in julia v0.5:

julia> a = ([1,2,3],[4,5,6],[7,8,9])
([1,2,3],[4,5,6],[7,8,9])

julia> [i for arr in a for i in arr]
9-element Array{Int64,1}:
 1
 2
 3
 4
 5
 6
 7
 8
 9