INTERFACE NewDerivatives2D (* SHAPE Attributes2D *);

IMPORT Neighborhood2D;

CONST N = 6;
  (*
    Number of derivatives *)
    
TYPE T = ARRAY [0..N-1] OF REAL;
  (*
    Set of derivatives at a texel *)

PROCEDURE FromNeighborhood(READONLY z: Neighborhood.T; VAR (*OUT*) a: T);
  (*
    Estimates the local derivatives at a texel from its neighborhood. *)

PROCEDURE EnergyAndStateForcesFromStateNeigborhood(
    READONLY z: ARRAY OF Neighborhood2D.T;       (* Multi-layer neighborhood *)
    energy: LocalEvaluator.T;                    (* Local energy evaluator *)
    VAR (*OUT*) E: LONGREAL;                     (* Computed local energy *)
    VAR (*OUT*) dEdz: ARRAY OF Neighborhood2D.T; (* Derivatives of "E" rel.to "z" *)
  );
  (*
    Computes the energy term associated with one texel, and
    its partial derivatives relative to the texel values, 
    from the texel's neighborhood. *)

TYPE
  Evaluator = OBJECT METHODS
      eval (READONLY p: ARRAY OF T; VAR E: LONGREAL; VAR dEdp: ARRAY OF T);
        (*
          Given the attributes in the neighborhood of a texel,
          in all layers, computes the corresponding  local term of the energy function,
          and its derivatives relative to each attribute. *) 

      print (wr: Wr.T);
        (*
          Prints a description of the energy evaluation function *)
    END;

BEGIN
END NewDerivatives2D.