open Common
module De = Determinant

type t

val make :
  ((int -> int -> Spin.t -> float) *
   (int -> int -> int -> int -> Spin.t -> Spin.t -> float) *
   (int -> int -> int -> int -> int -> int -> Spin.t -> Spin.t -> Spin.t -> float) option) list ->
   De.t -> De.t -> float list
(** [make integrals ki kj] Computes matrix elements for multiple operators between two Slater
    determinants, or returns zeros if the total degree of excitation exceeds 2.

    @param integrals A list of tuples containing one-electron, two-electron
           integrals, and optionally three-electron integrals, for each operator
    @param ki The initial Slater determinant.
    @param kj The final Slater determinant.
    
    @return A list of computed matrix elements or zeroes if the total excitation
            lebel (degree_a + degree_b) is greater than 2.
    
    Example usage:
    {[
      let integrals = [(one_e_integral, two_e_integral, None); (one_e_integral', two_e_integral', Some three_e_integral')] in
      let result = make integrals ki kj
    ]}
*)

val make_s2 : De.t -> De.t -> float
(** [make_s2 ki kj] computes the value of the $S^2$ operator for two determinants.

    @param ki The initial spin determinant.
    @param kj The final spin determinant.
    
    @return The computed value of the $S^2$ operator.
    
    Example usage:
    {[
      let s2_value = make_s2 ki kj
    ]}
    
*)


(** Computes matrix elements when the user knows they are non-zero.

    @param integrals A list of tuples containing one-electron, two-electron integrals, and optionally three-electron integrals.
    @param degree_a The degree of excitation in alpha spin orbitals.
    @param degree_b The degree of excitation in beta spin orbitals.
    @param ki The initial Slater determinant.
    @param kj The final Slater determinant.
    
    
    @return A list of matrix elements for multiple operators
    
    Example usage:
    {[
      let integrals = [(one_e_integral, two_e_integral, None); (one_e_integral, two_e_integral, Some three_e_integral)] in
      let result = non_zero integrals 1 1 ki kj
    ]}
    
*)
val non_zero :
  ((int -> int -> Spin.t -> float) *
   (int -> int -> int -> int -> Spin.t -> Spin.t -> float) *
   (int -> int -> int -> int -> int -> int -> Spin.t -> Spin.t -> Spin.t -> float) option) list ->
   int -> int -> De.t -> De.t -> float list