type t = { x: int ; y : int ; z : int ; tot : int }

let of_int_tuple t = 
  let result =
    match t with 
    | (x,y,z) -> { x ; y ; z ; tot=x+y+z }
  in
  assert (result.tot >= 0);
  result

let to_int_tuple { x ; y ; z ; _ } = (x,y,z) 

let get coord t =
  match coord with
  | Coordinate.X -> t.x
  | Coordinate.Y -> t.y
  | Coordinate.Z -> t.z

let incr coord t =
  match coord with
  | Coordinate.X -> { t with x = t.x+1 ; tot = t.tot+1 }
  | Coordinate.Y -> { t with y = t.y+1 ; tot = t.tot+1 }
  | Coordinate.Z -> { t with z = t.z+1 ; tot = t.tot+1 }

let decr coord t =
  (*
  let test _ = ()
      *)
  let test x =
    if x < 1 then
      invalid_arg "Angular_momentum.Powers.decr";
  in
  match coord with
  | Coordinate.X -> (test t.x ; { t with x = t.x-1 ; tot = t.tot-1 })
  | Coordinate.Y -> (test t.y ; { t with y = t.y-1 ; tot = t.tot-1 })
  | Coordinate.Z -> (test t.z ; { t with z = t.z-1 ; tot = t.tot-1 })