let partie_minimale mi mf =
    let d = Hashtbl.create 42 in
    Hashtbl.add d mi 0 ;

    let rec aux sphere dist =
    (∗ sphere : ensemble des motifs à distance dist de mi. ∗)
    if Hashtbl.mem d mf then Hashtbl.find d mf
    else if sphere = [] then failwith "motif final non accessible"
    else
    let sphere_suivante = strate d (dist+1) sphere in
    aux sphere_suivante (dist+1)
    in
    aux [mi] 0
;;