let adaptability_cstr_of_subtyping_cstr (Subtype (ct_x, ct_y)) =
let Alpha x, w_x = split_clock_type ct_x in
let Alpha y, w_y = split_clock_type ct_y in
if x = y then Adaptability (w_x, w_y)
else Adaptability (On (Var (C x), w_x), On (Var (C y), w_y))