(**
A spin-determinant is one of the two determinants in the Waller-Hartree
double determinant representation of a Slater determinant. It is represented
as a bit string and a phase factor.
*)

type t 

(** {1 Accessors}. *)

val phase : t -> Phase.t
(** Phase factor.
    @raise [Invalid_argument] if the spin-determinant is [None].
*)

val bitstring : t -> Z.t
(** Bit string.
    @raise [Invalid_argument] if the spin-determinant is [None].
*)

val is_none : t -> bool
(** Tests if a spin-determinant is [None]. *)


(** {1 Second quantization operators} *)
val vac : t
(** Vacuum state, [vac = Some ]{% $|\rangle$ %}  *)

val creation : int -> t -> t
(** [creation p] is the creation operator {% $a^\dagger_p$ %}. *)

val annihilation : int -> t -> t
(** [annihilation q] is the annihilation operator {% $a_q$ %}. *)

val of_list : int list -> t
(** Builds a spin-determinant from a list of orbital indices. If the creation of the
    spin-determinant is not possible because of Pauli's exclusion principle, a [None]
    spin-determinant is returned. *)

val to_list : t -> int list
(** Transforms a spin-determinant into a list of orbital indices. *)

(** {2 Printers}. *)

val pp_spindet : Format.formatter -> t -> unit


(** {2 Unit testing} *)

val test_case : unit -> (string * [> `Quick ] * (unit -> unit)) list