compute-grid-lines [grid, n, ns, orientation] = zip [h f, h g] | f = @n*v distr [@- distr [suffix [ns, n], v. [gap>> grid, orientation], orientation] | g = @v+ distr [f, v* [v- [dim>> grid, gap>> grid], reverse orientation]] | h = @(v+ @2/) @distr distr [id, gap>> grid]