exception AngularMomentumError of char

type t =
  | S | P | D | F | G | H | I | J | K | L | M | N | O

let of_char = function
  | 's' | 'S' -> S
  | 'p' | 'P' -> P
  | 'd' | 'D' -> D
  | 'f' | 'F' -> F
  | 'g' | 'G' -> G
  | 'h' | 'H' -> H
  | 'i' | 'I' -> I
  | 'j' | 'J' -> J
  | 'k' | 'K' -> K
  | 'l' | 'L' -> L
  | 'm' | 'M' -> M
  | 'n' | 'N' -> N
  | 'o' | 'O' -> O
  | c -> raise (AngularMomentumError c)

let to_string = function
  | S -> "S"
  | P -> "P"
  | D -> "D"
  | F -> "F"
  | G -> "G"
  | H -> "H"
  | I -> "I"
  | J -> "J"
  | K -> "K"
  | L -> "L"
  | M -> "M"
  | N -> "N"
  | O -> "O"