overlaps function
Whether two fitting cuts of one host overlap (spec 08 D8, for D17): each
starts more than wallJoin.linear before the other ends. Touching is not
overlap.
Implementation
bool overlaps((double, double) x, (double, double) y) =>
x.$1 < y.$2 - wallJoin.linear && y.$1 < x.$2 - wallJoin.linear;