a quick method for generating grid of matrix subscripts

f6.jl

function f6(xs, ys)
    lx, ly = length(xs), length(ys)
    lxly = lx*ly
    res = Array{Base.promote_eltype(xs, ys), 2}(lxly, 2)
    ind = 1
    while ind<=lxly
        @inbounds for x in xs
            res[ind] = x
            ind += 1
        end
    end
    for y in ys
        @inbounds for i=1:lx
           res[ind] = y
           ind += 1
        end
    end
end