The projections of the position a, from a up to its maximal projection.
- projectionsOf hd t a = List.map (fun (k : ℕ) => { toList := List.take ((↑a).length - k) ↑a }) (List.range ((↑a).length - (↑(projectionAt hd t a)).length + 1))
Used by mem_cyclicGoals