DEFINITION csuba_gen_abst_rev()
TYPE =
       ∀g:G
         .∀d1:C
           .∀c:C
             .∀u:T
               .csuba g c (CHead d1 (Bind Abst) u)
                 →(or
                      ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                      ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
BODY =
        assume g: G
        assume d1: C
        assume c: C
        assume u: T
        suppose H: csuba g c (CHead d1 (Bind Abst) u)
           assume y: C
           suppose H0: csuba g c y
             we proceed by induction on H0 to prove 
                eq C y (CHead d1 (Bind Abst) u)
                  →(or
                       ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                       ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
                case csuba_sort : n:nat ⇒
                   the thesis becomes 
                   ∀H1:eq C (CSort n) (CHead d1 (Bind Abst) u)
                     .or
                       ex2 C λd2:C.eq C (CSort n) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                       ex2_2 C T λd2:C.λu2:T.eq C (CSort n) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                      suppose H1: eq C (CSort n) (CHead d1 (Bind Abst) u)
                         (H2) 
                            we proceed by induction on H1 to prove 
                               <λ:C.Prop>
                                 CASE CHead d1 (Bind Abst) u OF
                                   CSort ⇒True
                                 | CHead   ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes <λ:C.Prop> CASE CSort n OF CSort ⇒True | CHead   ⇒False
                                     consider I
                                     we proved True
<λ:C.Prop> CASE CSort n OF CSort ⇒True | CHead   ⇒False

                               <λ:C.Prop>
                                 CASE CHead d1 (Bind Abst) u OF
                                   CSort ⇒True
                                 | CHead   ⇒False
                         end of H2
                         consider H2
                         we proved 
                            <λ:C.Prop>
                              CASE CHead d1 (Bind Abst) u OF
                                CSort ⇒True
                              | CHead   ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2 C λd2:C.eq C (CSort n) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                              ex2_2 C T λd2:C.λu2:T.eq C (CSort n) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                         we proved 
                            or
                              ex2 C λd2:C.eq C (CSort n) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                              ex2_2 C T λd2:C.λu2:T.eq C (CSort n) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1

                         ∀H1:eq C (CSort n) (CHead d1 (Bind Abst) u)
                           .or
                             ex2 C λd2:C.eq C (CSort n) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                             ex2_2 C T λd2:C.λu2:T.eq C (CSort n) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                case csuba_head : c1:C c2:C H1:csuba g c1 c2 k:K u0:T ⇒
                   the thesis becomes 
                   ∀H3:eq C (CHead c2 k u0) (CHead d1 (Bind Abst) u)
                     .or
                       ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                       ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                   (H2) by induction hypothesis we know 
                      eq C c2 (CHead d1 (Bind Abst) u)
                        →(or
                             ex2 C λd2:C.eq C c1 (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                             ex2_2 C T λd2:C.λu2:T.eq C c1 (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
                      suppose H3: eq C (CHead c2 k u0) (CHead d1 (Bind Abst) u)
                         (H4) 
                            by (f_equal . . . . . H3)
                            we proved 
                               eq
                                 C
                                 <λ:C.C> CASE CHead c2 k u0 OF CSort ⇒c2 | CHead c0  ⇒c0
                                 <λ:C.C> CASE CHead d1 (Bind Abst) u OF CSort ⇒c2 | CHead c0  ⇒c0

                               eq
                                 C
                                 λe:C.<λ:C.C> CASE e OF CSort ⇒c2 | CHead c0  ⇒c0 (CHead c2 k u0)
                                 λe:C.<λ:C.C> CASE e OF CSort ⇒c2 | CHead c0  ⇒c0 (CHead d1 (Bind Abst) u)
                         end of H4
                         (h1) 
                            (H5) 
                               by (f_equal . . . . . H3)
                               we proved 
                                  eq
                                    K
                                    <λ:C.K> CASE CHead c2 k u0 OF CSort ⇒k | CHead  k0 ⇒k0
                                    <λ:C.K> CASE CHead d1 (Bind Abst) u OF CSort ⇒k | CHead  k0 ⇒k0

                                  eq
                                    K
                                    λe:C.<λ:C.K> CASE e OF CSort ⇒k | CHead  k0 ⇒k0 (CHead c2 k u0)
                                    λe:C.<λ:C.K> CASE e OF CSort ⇒k | CHead  k0 ⇒k0 (CHead d1 (Bind Abst) u)
                            end of H5
                            (h1) 
                               (H6) 
                                  by (f_equal . . . . . H3)
                                  we proved 
                                     eq
                                       T
                                       <λ:C.T> CASE CHead c2 k u0 OF CSort ⇒u0 | CHead   t⇒t
                                       <λ:C.T> CASE CHead d1 (Bind Abst) u OF CSort ⇒u0 | CHead   t⇒t

                                     eq
                                       T
                                       λe:C.<λ:C.T> CASE e OF CSort ⇒u0 | CHead   t⇒t (CHead c2 k u0)
                                       λe:C.<λ:C.T> CASE e OF CSort ⇒u0 | CHead   t⇒t (CHead d1 (Bind Abst) u)
                               end of H6
                                suppose H7: eq K k (Bind Abst)
                                suppose H8: eq C c2 d1
                                  (h1) 
                                     (H10) 
                                        we proceed by induction on H8 to prove csuba g c1 d1
                                           case refl_equal : ⇒
                                              the thesis becomes the hypothesis H1
csuba g c1 d1
                                     end of H10
                                     by (refl_equal . .)
                                     we proved eq C (CHead c1 (Bind Abst) u) (CHead c1 (Bind Abst) u)
                                     by (ex_intro2 . . . . previous H10)
                                     we proved 
                                        ex2
                                          C
                                          λd2:C.eq C (CHead c1 (Bind Abst) u) (CHead d2 (Bind Abst) u)
                                          λd2:C.csuba g d2 d1
                                     by (or_introl . . previous)
                                     we proved 
                                        or
                                          ex2
                                            C
                                            λd2:C.eq C (CHead c1 (Bind Abst) u) (CHead d2 (Bind Abst) u)
                                            λd2:C.csuba g d2 d1
                                          ex2_2
                                            C
                                            T
                                            λd2:C.λu2:T.eq C (CHead c1 (Bind Abst) u) (CHead d2 (Bind Void) u2)
                                            λd2:C.λ:T.csuba g d2 d1
                                     by (eq_ind_r . . . previous . H7)

                                        or
                                          ex2 C λd2:C.eq C (CHead c1 k u) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                                          ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                                  end of h1
                                  (h2) 
                                     consider H6
                                     we proved 
                                        eq
                                          T
                                          <λ:C.T> CASE CHead c2 k u0 OF CSort ⇒u0 | CHead   t⇒t
                                          <λ:C.T> CASE CHead d1 (Bind Abst) u OF CSort ⇒u0 | CHead   t⇒t
eq T u0 u
                                  end of h2
                                  by (eq_ind_r . . . h1 . h2)
                                  we proved 
                                     or
                                       ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                                       ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1

                                  eq K k (Bind Abst)
                                    →(eq C c2 d1
                                         →(or
                                              ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                                              ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1))
                            end of h1
                            (h2) 
                               consider H5
                               we proved 
                                  eq
                                    K
                                    <λ:C.K> CASE CHead c2 k u0 OF CSort ⇒k | CHead  k0 ⇒k0
                                    <λ:C.K> CASE CHead d1 (Bind Abst) u OF CSort ⇒k | CHead  k0 ⇒k0
eq K k (Bind Abst)
                            end of h2
                            by (h1 h2)

                               eq C c2 d1
                                 →(or
                                      ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                                      ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
                         end of h1
                         (h2) 
                            consider H4
                            we proved 
                               eq
                                 C
                                 <λ:C.C> CASE CHead c2 k u0 OF CSort ⇒c2 | CHead c0  ⇒c0
                                 <λ:C.C> CASE CHead d1 (Bind Abst) u OF CSort ⇒c2 | CHead c0  ⇒c0
eq C c2 d1
                         end of h2
                         by (h1 h2)
                         we proved 
                            or
                              ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                              ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1

                         ∀H3:eq C (CHead c2 k u0) (CHead d1 (Bind Abst) u)
                           .or
                             ex2 C λd2:C.eq C (CHead c1 k u0) (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                             ex2_2 C T λd2:C.λu2:T.eq C (CHead c1 k u0) (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
                case csuba_void : c1:C c2:C H1:csuba g c1 c2 b:B H3:not (eq B b Void) u1:T u2:T ⇒
                   the thesis becomes 
                   ∀H4:eq C (CHead c2 (Bind b) u2) (CHead d1 (Bind Abst) u)
                     .or
                       ex2
                         C
                         λd2:C.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Abst) u)
                         λd2:C.csuba g d2 d1
                       ex2_2
                         C
                         T
                         λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                         λd2:C.λ:T.csuba g d2 d1
                   (H2) by induction hypothesis we know 
                      eq C c2 (CHead d1 (Bind Abst) u)
                        →(or
                             ex2 C λd2:C.eq C c1 (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                             ex2_2 C T λd2:C.λu2:T.eq C c1 (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
                      suppose H4: eq C (CHead c2 (Bind b) u2) (CHead d1 (Bind Abst) u)
                         (H5) 
                            by (f_equal . . . . . H4)
                            we proved 
                               eq
                                 C
                                 <λ:C.C> CASE CHead c2 (Bind b) u2 OF CSort ⇒c2 | CHead c0  ⇒c0
                                 <λ:C.C> CASE CHead d1 (Bind Abst) u OF CSort ⇒c2 | CHead c0  ⇒c0

                               eq
                                 C
                                 λe:C.<λ:C.C> CASE e OF CSort ⇒c2 | CHead c0  ⇒c0 (CHead c2 (Bind b) u2)
                                 λe:C.<λ:C.C> CASE e OF CSort ⇒c2 | CHead c0  ⇒c0 (CHead d1 (Bind Abst) u)
                         end of H5
                         (h1) 
                            (H6) 
                               by (f_equal . . . . . H4)
                               we proved 
                                  eq
                                    B
                                    <λ:C.B>
                                      CASE CHead c2 (Bind b) u2 OF
                                        CSort ⇒b
                                      | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b
                                    <λ:C.B>
                                      CASE CHead d1 (Bind Abst) u OF
                                        CSort ⇒b
                                      | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b

                                  eq
                                    B
                                    λe:C.<λ:C.B> CASE e OF CSort ⇒b | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b
                                      CHead c2 (Bind b) u2
                                    λe:C.<λ:C.B> CASE e OF CSort ⇒b | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b
                                      CHead d1 (Bind Abst) u
                            end of H6
                            (H8) 
                               consider H6
                               we proved 
                                  eq
                                    B
                                    <λ:C.B>
                                      CASE CHead c2 (Bind b) u2 OF
                                        CSort ⇒b
                                      | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b
                                    <λ:C.B>
                                      CASE CHead d1 (Bind Abst) u OF
                                        CSort ⇒b
                                      | CHead  k ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒b
eq B b Abst
                            end of H8
                            suppose H9: eq C c2 d1
                               (H12) 
                                  we proceed by induction on H9 to prove csuba g c1 d1
                                     case refl_equal : ⇒
                                        the thesis becomes the hypothesis H1
csuba g c1 d1
                               end of H12
                               by (refl_equal . .)
                               we proved eq C (CHead c1 (Bind Void) u1) (CHead c1 (Bind Void) u1)
                               by (ex2_2_intro . . . . . . previous H12)
                               we proved 
                                  ex2_2
                                    C
                                    T
                                    λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                                    λd2:C.λ:T.csuba g d2 d1
                               by (or_intror . . previous)
                               we proved 
                                  or
                                    ex2
                                      C
                                      λd2:C.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Abst) u)
                                      λd2:C.csuba g d2 d1
                                    ex2_2
                                      C
                                      T
                                      λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                                      λd2:C.λ:T.csuba g d2 d1

                               eq C c2 d1
                                 →(or
                                      ex2
                                        C
                                        λd2:C.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Abst) u)
                                        λd2:C.csuba g d2 d1
                                      ex2_2
                                        C
                                        T
                                        λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                                        λd2:C.λ:T.csuba g d2 d1)
                         end of h1
                         (h2) 
                            consider H5
                            we proved 
                               eq
                                 C
                                 <λ:C.C> CASE CHead c2 (Bind b) u2 OF CSort ⇒c2 | CHead c0  ⇒c0
                                 <λ:C.C> CASE CHead d1 (Bind Abst) u OF CSort ⇒c2 | CHead c0  ⇒c0
eq C c2 d1
                         end of h2
                         by (h1 h2)
                         we proved 
                            or
                              ex2
                                C
                                λd2:C.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Abst) u)
                                λd2:C.csuba g d2 d1
                              ex2_2
                                C
                                T
                                λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                                λd2:C.λ:T.csuba g d2 d1

                         ∀H4:eq C (CHead c2 (Bind b) u2) (CHead d1 (Bind Abst) u)
                           .or
                             ex2
                               C
                               λd2:C.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Abst) u)
                               λd2:C.csuba g d2 d1
                             ex2_2
                               C
                               T
                               λd2:C.λu3:T.eq C (CHead c1 (Bind Void) u1) (CHead d2 (Bind Void) u3)
                               λd2:C.λ:T.csuba g d2 d1
                case csuba_abst : c1:C c2:C :csuba g c1 c2 t:T a:A :arity g c1 t (asucc g a) u0:T :arity g c2 u0 a ⇒
                   the thesis becomes 
                   ∀H5:eq C (CHead c2 (Bind Abbr) u0) (CHead d1 (Bind Abst) u)
                     .or
                       ex2
                         C
                         λd2:C.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Abst) u)
                         λd2:C.csuba g d2 d1
                       ex2_2
                         C
                         T
                         λd2:C.λu2:T.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Void) u2)
                         λd2:C.λ:T.csuba g d2 d1
                   () by induction hypothesis we know 
                      eq C c2 (CHead d1 (Bind Abst) u)
                        →(or
                             ex2 C λd2:C.eq C c1 (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                             ex2_2 C T λd2:C.λu2:T.eq C c1 (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
                      suppose H5: eq C (CHead c2 (Bind Abbr) u0) (CHead d1 (Bind Abst) u)
                         (H6) 
                            we proceed by induction on H5 to prove 
                               <λ:C.Prop>
                                 CASE CHead d1 (Bind Abst) u OF
                                   CSort ⇒False
                                 | CHead  k ⇒
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind b⇒<λ:B.Prop> CASE b OF Abbr⇒True | Abst⇒False | Void⇒False
                                         | Flat ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:C.Prop>
                                    CASE CHead c2 (Bind Abbr) u0 OF
                                      CSort ⇒False
                                    | CHead  k ⇒
                                          <λ:K.Prop>
                                            CASE k OF
                                              Bind b⇒<λ:B.Prop> CASE b OF Abbr⇒True | Abst⇒False | Void⇒False
                                            | Flat ⇒False
                                     consider I
                                     we proved True

                                        <λ:C.Prop>
                                          CASE CHead c2 (Bind Abbr) u0 OF
                                            CSort ⇒False
                                          | CHead  k ⇒
                                                <λ:K.Prop>
                                                  CASE k OF
                                                    Bind b⇒<λ:B.Prop> CASE b OF Abbr⇒True | Abst⇒False | Void⇒False
                                                  | Flat ⇒False

                               <λ:C.Prop>
                                 CASE CHead d1 (Bind Abst) u OF
                                   CSort ⇒False
                                 | CHead  k ⇒
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind b⇒<λ:B.Prop> CASE b OF Abbr⇒True | Abst⇒False | Void⇒False
                                         | Flat ⇒False
                         end of H6
                         consider H6
                         we proved 
                            <λ:C.Prop>
                              CASE CHead d1 (Bind Abst) u OF
                                CSort ⇒False
                              | CHead  k ⇒
                                    <λ:K.Prop>
                                      CASE k OF
                                        Bind b⇒<λ:B.Prop> CASE b OF Abbr⇒True | Abst⇒False | Void⇒False
                                      | Flat ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2
                                C
                                λd2:C.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Abst) u)
                                λd2:C.csuba g d2 d1
                              ex2_2
                                C
                                T
                                λd2:C.λu2:T.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Void) u2)
                                λd2:C.λ:T.csuba g d2 d1
                         we proved 
                            or
                              ex2
                                C
                                λd2:C.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Abst) u)
                                λd2:C.csuba g d2 d1
                              ex2_2
                                C
                                T
                                λd2:C.λu2:T.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Void) u2)
                                λd2:C.λ:T.csuba g d2 d1

                         ∀H5:eq C (CHead c2 (Bind Abbr) u0) (CHead d1 (Bind Abst) u)
                           .or
                             ex2
                               C
                               λd2:C.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Abst) u)
                               λd2:C.csuba g d2 d1
                             ex2_2
                               C
                               T
                               λd2:C.λu2:T.eq C (CHead c1 (Bind Abst) t) (CHead d2 (Bind Void) u2)
                               λd2:C.λ:T.csuba g d2 d1
             we proved 
                eq C y (CHead d1 (Bind Abst) u)
                  →(or
                       ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                       ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)
          we proved 
             ∀y:C
               .csuba g c y
                 →(eq C y (CHead d1 (Bind Abst) u)
                      →(or
                           ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                           ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1))
          by (insert_eq . . . . previous H)
          we proved 
             or
               ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
               ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1
       we proved 
          ∀g:G
            .∀d1:C
              .∀c:C
                .∀u:T
                  .csuba g c (CHead d1 (Bind Abst) u)
                    →(or
                         ex2 C λd2:C.eq C c (CHead d2 (Bind Abst) u) λd2:C.csuba g d2 d1
                         ex2_2 C T λd2:C.λu2:T.eq C c (CHead d2 (Bind Void) u2) λd2:C.λ:T.csuba g d2 d1)