julia> a = [1 2];
1x2 Array{Int64,2}:
 1  2
julia> b = [3 4];
1x2 Array{Int64,2}:
 3  4
julia> [a b]
1x4 Array{Int64,2}:
 1  2  3  4
julia> [a; b]
2x2 Array{Int64,2}:
 1  2
 3  4
julia> [a' b']
2x2 Array{Int64,2}:
 1  3
 2  4