DEFINITION pr3_iso_appls_bind()
TYPE =
       b:B
         .not (eq B b Abst)
           vs:TList
                .u:T
                  .t:T
                    .let u1 := THeads (Flat Appl) vs (THead (Bind b) u t)
                    in c:C
                           .u2:T
                             .pr3 c u1 u2
                               ((iso u1 u2)P:Prop.P
                                    (pr3
                                         c
                                         THead (Bind b) u (THeads (Flat Appl) (lifts (S OO vs) t)
                                         u2))
BODY =
        assume bB
        suppose Hnot (eq B b Abst)
        assume vsTList
          (h1
              assume uT
              assume tT
                we must prove 
                      let u1 := THeads (Flat ApplTNil (THead (Bind b) u t)
                      in c:C
                             .u2:T
                               .pr3 c u1 u2
                                 ((iso u1 u2)P:Prop.P
                                      (pr3
                                           c
                                           THead
                                             Bind b
                                             u
                                             THeads (Flat Appl) (lifts (S OO TNil) t
                                           u2))
                or equivalently 
                      c:C
                        .u2:T
                          .pr3 c (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                            (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                                   P:Prop.P
                                 (pr3
                                      c
                                      THead
                                        Bind b
                                        u
                                        THeads (Flat Appl) (lifts (S OO TNil) t
                                      u2))
                 assume cC
                 assume u2T
                   we must prove 
                         pr3 c (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                           (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                                  P:Prop.P
                                (pr3
                                     c
                                     THead
                                       Bind b
                                       u
                                       THeads (Flat Appl) (lifts (S OO TNil) t
                                     u2))
                   or equivalently 
                         pr3 c (THead (Bind b) u t) u2
                           (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                                  P:Prop.P
                                (pr3
                                     c
                                     THead
                                       Bind b
                                       u
                                       THeads (Flat Appl) (lifts (S OO TNil) t
                                     u2))
                   suppose H0pr3 c (THead (Bind b) u t) u2
                      we must prove 
                            iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                                P:Prop.P
                              (pr3
                                   c
                                   THead
                                     Bind b
                                     u
                                     THeads (Flat Appl) (lifts (S OO TNil) t
                                   u2)
                      or equivalently 
                            (iso (THead (Bind b) u t) u2)P:Prop.P
                              (pr3
                                   c
                                   THead
                                     Bind b
                                     u
                                     THeads (Flat Appl) (lifts (S OO TNil) t
                                   u2)
                      suppose (iso (THead (Bind b) u t) u2)P:Prop.P
                         consider H0
                         we proved pr3 c (THead (Bind b) u t) u2
                         that is equivalent to 
                            pr3
                              c
                              THead
                                Bind b
                                u
                                THeads (Flat Appl) (lifts (S OO TNil) t
                              u2
                      we proved 
                         (iso (THead (Bind b) u t) u2)P:Prop.P
                           (pr3
                                c
                                THead
                                  Bind b
                                  u
                                  THeads (Flat Appl) (lifts (S OO TNil) t
                                u2)
                      that is equivalent to 
                         iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                             P:Prop.P
                           (pr3
                                c
                                THead
                                  Bind b
                                  u
                                  THeads (Flat Appl) (lifts (S OO TNil) t
                                u2)
                   we proved 
                      pr3 c (THead (Bind b) u t) u2
                        (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                               P:Prop.P
                             (pr3
                                  c
                                  THead
                                    Bind b
                                    u
                                    THeads (Flat Appl) (lifts (S OO TNil) t
                                  u2))
                   that is equivalent to 
                      pr3 c (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                        (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                               P:Prop.P
                             (pr3
                                  c
                                  THead
                                    Bind b
                                    u
                                    THeads (Flat Appl) (lifts (S OO TNil) t
                                  u2))
                we proved 
                   c:C
                     .u2:T
                       .pr3 c (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                         (iso (THeads (Flat ApplTNil (THead (Bind b) u t)) u2
                                P:Prop.P
                              (pr3
                                   c
                                   THead
                                     Bind b
                                     u
                                     THeads (Flat Appl) (lifts (S OO TNil) t
                                   u2))
                that is equivalent to 
                   let u1 := THeads (Flat ApplTNil (THead (Bind b) u t)
                   in c:C
                          .u2:T
                            .pr3 c u1 u2
                              ((iso u1 u2)P:Prop.P
                                   (pr3
                                        c
                                        THead
                                          Bind b
                                          u
                                          THeads (Flat Appl) (lifts (S OO TNil) t
                                        u2))

                u:T
                  .t:T
                    .let u1 := THeads (Flat ApplTNil (THead (Bind b) u t)
                    in c:C
                           .u2:T
                             .pr3 c u1 u2
                               ((iso u1 u2)P:Prop.P
                                    (pr3
                                         c
                                         THead
                                           Bind b
                                           u
                                           THeads (Flat Appl) (lifts (S OO TNil) t
                                         u2))
          end of h1
          (h2
              assume tsTList
              assume tT
                we must prove 
                      u:T
                          .t0:T
                            .let u1 := THeads (Flat Appl) ts (THead (Bind b) u t0)
                            in c:C
                                   .u2:T
                                     .pr3 c u1 u2
                                       ((iso u1 u2)P:Prop.P
                                            (pr3
                                                 c
                                                 THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                                 u2))
                        u:T
                             .t0:T
                               .let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                               in c:C
                                      .u2:T
                                        .pr3 c u1 u2
                                          ((iso u1 u2)P:Prop.P
                                               (pr3
                                                    c
                                                    THead
                                                      Bind b
                                                      u
                                                      THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                                    u2))
                or equivalently 
                      u:T
                          .t0:T
                            .c:C
                              .u2:T
                                .pr3 c (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                                  (iso (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                                         P:Prop.P
                                       (pr3
                                            c
                                            THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                            u2))
                        u:T
                             .t0:T
                               .let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                               in c:C
                                      .u2:T
                                        .pr3 c u1 u2
                                          ((iso u1 u2)P:Prop.P
                                               (pr3
                                                    c
                                                    THead
                                                      Bind b
                                                      u
                                                      THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                                    u2))
                 suppose H0
                    u:T
                      .t0:T
                        .c:C
                          .u2:T
                            .pr3 c (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                              (iso (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                                     P:Prop.P
                                   (pr3
                                        c
                                        THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                        u2))
                 assume uT
                 assume t0T
                   we must prove 
                         let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                         in c:C
                                .u2:T
                                  .pr3 c u1 u2
                                    ((iso u1 u2)P:Prop.P
                                         (pr3
                                              c
                                              THead
                                                Bind b
                                                u
                                                THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                              u2))
                   or equivalently 
                         c:C
                           .u2:T
                             .pr3 c (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                               (iso (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                                      P:Prop.P
                                    (pr3
                                         c
                                         THead
                                           Bind b
                                           u
                                           THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                         u2))
                    assume cC
                    assume u2T
                    suppose H1pr3 c (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                    suppose H2
                       iso (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                         P:Prop.P
                      (h1
                         (h1
                            (H3
                               by (theads_tapp . . . .)
                               we proved 
                                  eq
                                    T
                                    THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                                    THeads
                                      Flat Appl
                                      ts
                                      THead (Flat Appl) t (THead (Bind b) u t0)
                               we proceed by induction on the previous result to prove 
                                  pr3
                                    c
                                    THeads
                                      Flat Appl
                                      ts
                                      THead (Flat Appl) t (THead (Bind b) u t0)
                                    u2
                                  case refl_equal : 
                                     the thesis becomes the hypothesis H1

                                  pr3
                                    c
                                    THeads
                                      Flat Appl
                                      ts
                                      THead (Flat Appl) t (THead (Bind b) u t0)
                                    u2
                            end of H3
                            (H4
                               by (theads_tapp . . . .)
                               we proved 
                                  eq
                                    T
                                    THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                                    THeads
                                      Flat Appl
                                      ts
                                      THead (Flat Appl) t (THead (Bind b) u t0)
                               we proceed by induction on the previous result to prove 
                                  (iso
                                      THeads
                                        Flat Appl
                                        ts
                                        THead (Flat Appl) t (THead (Bind b) u t0)
                                      u2)
                                    P:Prop.P
                                  case refl_equal : 
                                     the thesis becomes the hypothesis H2

                                  (iso
                                      THeads
                                        Flat Appl
                                        ts
                                        THead (Flat Appl) t (THead (Bind b) u t0)
                                      u2)
                                    P:Prop.P
                            end of H4
                             suppose 
                                u0:T
                                  .t1:T
                                    .c0:C
                                      .u3:T
                                        .pr3 c0 (THeads (Flat ApplTNil (THead (Bind b) u0 t1)) u3
                                          (iso (THeads (Flat ApplTNil (THead (Bind b) u0 t1)) u3
                                                 P:Prop.P
                                               (pr3
                                                    c0
                                                    THead (Bind b) u0 (THeads (Flat Appl) (lifts (S OO TNil) t1)
                                                    u3))
                             suppose H6
                                pr3
                                  c
                                  THeads
                                    Flat Appl
                                    TNil
                                    THead (Flat Appl) t (THead (Bind b) u t0)
                                  u2
                             suppose H7
                                (iso
                                    THeads
                                      Flat Appl
                                      TNil
                                      THead (Flat Appl) t (THead (Bind b) u t0)
                                    u2)
                                  P:Prop.P
                               (h1
                                  consider H6
                                  we proved 
                                     pr3
                                       c
                                       THeads
                                         Flat Appl
                                         TNil
                                         THead (Flat Appl) t (THead (Bind b) u t0)
                                       u2
pr3 c (THead (Flat Appl) t (THead (Bind b) u t0)) u2
                               end of h1
                               (h2
                                  consider H7
                                  we proved 
                                     (iso
                                         THeads
                                           Flat Appl
                                           TNil
                                           THead (Flat Appl) t (THead (Bind b) u t0)
                                         u2)
                                       P:Prop.P
(iso (THead (Flat Appl) t (THead (Bind b) u t0)) u2)P:Prop.P
                               end of h2
                               by (pr3_iso_appl_bind . H . . . . . h1 h2)
                               we proved pr3 c (THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)) u2
                               that is equivalent to 
                                  pr3
                                    c
                                    THead
                                      Bind b
                                      u
                                      THeads
                                        Flat Appl
                                        lifts (S OO TNil
                                        THead (Flat Appl) (lift (S OO t) t0
                                    u2

                               u0:T
                                   .t1:T
                                     .c0:C
                                       .u3:T
                                         .pr3 c0 (THeads (Flat ApplTNil (THead (Bind b) u0 t1)) u3
                                           (iso (THeads (Flat ApplTNil (THead (Bind b) u0 t1)) u3
                                                  P:Prop.P
                                                (pr3
                                                     c0
                                                     THead (Bind b) u0 (THeads (Flat Appl) (lifts (S OO TNil) t1)
                                                     u3))
                                 ((pr3
                                        c
                                        THeads
                                          Flat Appl
                                          TNil
                                          THead (Flat Appl) t (THead (Bind b) u t0)
                                        u2)
                                      ((iso
                                               THeads
                                                 Flat Appl
                                                 TNil
                                                 THead (Flat Appl) t (THead (Bind b) u t0)
                                               u2)
                                             P:Prop.P
                                           (pr3
                                                c
                                                THead
                                                  Bind b
                                                  u
                                                  THeads
                                                    Flat Appl
                                                    lifts (S OO TNil
                                                    THead (Flat Appl) (lift (S OO t) t0
                                                u2)))
                             assume t1T
                             assume ts0TList
                                suppose 
                                   u0:T
                                       .t2:T
                                         .c0:C
                                           .u3:T
                                             .pr3 c0 (THeads (Flat Appl) ts0 (THead (Bind b) u0 t2)) u3
                                               ((iso (THeads (Flat Appl) ts0 (THead (Bind b) u0 t2)) u3)P:Prop.P
                                                    pr3 c0 (THead (Bind b) u0 (THeads (Flat Appl) (lifts (S OO ts0) t2)) u3)
                                     ((pr3
                                            c
                                            THeads
                                              Flat Appl
                                              ts0
                                              THead (Flat Appl) t (THead (Bind b) u t0)
                                            u2)
                                          ((iso
                                                   THeads
                                                     Flat Appl
                                                     ts0
                                                     THead (Flat Appl) t (THead (Bind b) u t0)
                                                   u2)
                                                 P:Prop.P
                                               (pr3
                                                    c
                                                    THead
                                                      Bind b
                                                      u
                                                      THeads
                                                        Flat Appl
                                                        lifts (S OO ts0
                                                        THead (Flat Appl) (lift (S OO t) t0
                                                    u2)))
                                suppose H5
                                   u0:T
                                     .t2:T
                                       .c0:C
                                         .u3:T
                                           .pr3 c0 (THeads (Flat Appl) (TCons t1 ts0) (THead (Bind b) u0 t2)) u3
                                             (iso (THeads (Flat Appl) (TCons t1 ts0) (THead (Bind b) u0 t2)) u3
                                                    P:Prop.P
                                                  (pr3
                                                       c0
                                                       THead
                                                         Bind b
                                                         u0
                                                         THeads (Flat Appl) (lifts (S OO (TCons t1 ts0)) t2
                                                       u3))
                                suppose H6
                                   pr3
                                     c
                                     THeads
                                       Flat Appl
                                       TCons t1 ts0
                                       THead (Flat Appl) t (THead (Bind b) u t0)
                                     u2
                                suppose H7
                                   (iso
                                       THeads
                                         Flat Appl
                                         TCons t1 ts0
                                         THead (Flat Appl) t (THead (Bind b) u t0)
                                       u2)
                                     P:Prop.P
                                  (h1
                                     by (pr3_iso_appls_appl_bind . H . . . . . . H6 H7)

                                        pr3
                                          c
                                          THeads
                                            Flat Appl
                                            TCons t1 ts0
                                            THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)
                                          u2
                                  end of h1
                                  (h2
                                      suppose H8
                                         iso
                                           THeads
                                             Flat Appl
                                             TCons t1 ts0
                                             THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)
                                           u2
                                      assume PProp
                                        by (iso_head . . . . .)
                                        we proved 
                                           iso
                                             THead
                                               Flat Appl
                                               t1
                                               THeads
                                                 Flat Appl
                                                 ts0
                                                 THead (Flat Appl) t (THead (Bind b) u t0)
                                             THead
                                               Flat Appl
                                               t1
                                               THeads
                                                 Flat Appl
                                                 ts0
                                                 THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)
                                        that is equivalent to 
                                           iso
                                             THeads
                                               Flat Appl
                                               TCons t1 ts0
                                               THead (Flat Appl) t (THead (Bind b) u t0)
                                             THeads
                                               Flat Appl
                                               TCons t1 ts0
                                               THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)
                                        by (iso_trans . . previous . H8)
                                        we proved 
                                           iso
                                             THeads
                                               Flat Appl
                                               TCons t1 ts0
                                               THead (Flat Appl) t (THead (Bind b) u t0)
                                             u2
                                        by (H7 previous .)
                                        we proved P

                                        (iso
                                            THeads
                                              Flat Appl
                                              TCons t1 ts0
                                              THead (Bind b) u (THead (Flat Appl) (lift (S OO t) t0)
                                            u2)
                                          P:Prop.P
                                  end of h2
                                  by (H5 . . . . h1 h2)
                                  we proved 
                                     pr3
                                       c
                                       THead
                                         Bind b
                                         u
                                         THeads
                                           Flat Appl
                                           lifts (S OO (TCons t1 ts0)
                                           THead (Flat Appl) (lift (S OO t) t0
                                       u2

                                  H5:u0:T
                                             .t2:T
                                               .c0:C
                                                 .u3:T
                                                   .pr3 c0 (THeads (Flat Appl) (TCons t1 ts0) (THead (Bind b) u0 t2)) u3
                                                     (iso (THeads (Flat Appl) (TCons t1 ts0) (THead (Bind b) u0 t2)) u3
                                                            P:Prop.P
                                                          (pr3
                                                               c0
                                                               THead
                                                                 Bind b
                                                                 u0
                                                                 THeads (Flat Appl) (lifts (S OO (TCons t1 ts0)) t2
                                                               u3))
                                    .H6:pr3
                                               c
                                               THeads
                                                 Flat Appl
                                                 TCons t1 ts0
                                                 THead (Flat Appl) t (THead (Bind b) u t0)
                                               u2
                                      .H7:(iso
                                                   THeads
                                                     Flat Appl
                                                     TCons t1 ts0
                                                     THead (Flat Appl) t (THead (Bind b) u t0)
                                                   u2)
                                                 P:Prop.P
                                        .pr3
                                          c
                                          THead
                                            Bind b
                                            u
                                            THeads
                                              Flat Appl
                                              lifts (S OO (TCons t1 ts0)
                                              THead (Flat Appl) (lift (S OO t) t0
                                          u2
                            by (previous . H0 H3 H4)

                               pr3
                                 c
                                 THead
                                   Bind b
                                   u
                                   THeads
                                     Flat Appl
                                     lifts (S OO ts
                                     THead (Flat Appl) (lift (S OO t) t0
                                 u2
                         end of h1
                         (h2
                            by (theads_tapp . . . .)

                               eq
                                 T
                                 THeads
                                   Flat Appl
                                   TApp (lifts (S OO ts) (lift (S OO t)
                                   t0
                                 THeads
                                   Flat Appl
                                   lifts (S OO ts
                                   THead (Flat Appl) (lift (S OO t) t0
                         end of h2
                         by (eq_ind_r . . . h1 . h2)

                            pr3
                              c
                              THead
                                Bind b
                                u
                                THeads
                                  Flat Appl
                                  TApp (lifts (S OO ts) (lift (S OO t)
                                  t0
                              u2
                      end of h1
                      (h2
                         by (lifts_tapp . . . .)

                            eq
                              TList
                              lifts (S OO (TApp ts t)
                              TApp (lifts (S OO ts) (lift (S OO t)
                      end of h2
                      by (eq_ind_r . . . h1 . h2)
                      we proved 
                         pr3
                           c
                           THead
                             Bind b
                             u
                             THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                           u2
                   we proved 
                      c:C
                        .u2:T
                          .pr3 c (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                            (iso (THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)) u2
                                   P:Prop.P
                                 (pr3
                                      c
                                      THead
                                        Bind b
                                        u
                                        THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                      u2))
                   that is equivalent to 
                      let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                      in c:C
                             .u2:T
                               .pr3 c u1 u2
                                 ((iso u1 u2)P:Prop.P
                                      (pr3
                                           c
                                           THead
                                             Bind b
                                             u
                                             THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                           u2))
                we proved 
                   u:T
                       .t0:T
                         .c:C
                           .u2:T
                             .pr3 c (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                               (iso (THeads (Flat Appl) ts (THead (Bind b) u t0)) u2
                                      P:Prop.P
                                    (pr3
                                         c
                                         THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                         u2))
                     u:T
                          .t0:T
                            .let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                            in c:C
                                   .u2:T
                                     .pr3 c u1 u2
                                       ((iso u1 u2)P:Prop.P
                                            (pr3
                                                 c
                                                 THead
                                                   Bind b
                                                   u
                                                   THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                                 u2))
                that is equivalent to 
                   u:T
                       .t0:T
                         .let u1 := THeads (Flat Appl) ts (THead (Bind b) u t0)
                         in c:C
                                .u2:T
                                  .pr3 c u1 u2
                                    ((iso u1 u2)P:Prop.P
                                         (pr3
                                              c
                                              THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                              u2))
                     u:T
                          .t0:T
                            .let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                            in c:C
                                   .u2:T
                                     .pr3 c u1 u2
                                       ((iso u1 u2)P:Prop.P
                                            (pr3
                                                 c
                                                 THead
                                                   Bind b
                                                   u
                                                   THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                                 u2))

                ts:TList
                  .t:T
                    .u:T
                        .t0:T
                          .let u1 := THeads (Flat Appl) ts (THead (Bind b) u t0)
                          in c:C
                                 .u2:T
                                   .pr3 c u1 u2
                                     ((iso u1 u2)P:Prop.P
                                          (pr3
                                               c
                                               THead (Bind b) u (THeads (Flat Appl) (lifts (S OO ts) t0)
                                               u2))
                      u:T
                           .t0:T
                             .let u1 := THeads (Flat Appl) (TApp ts t) (THead (Bind b) u t0)
                             in c:C
                                    .u2:T
                                      .pr3 c u1 u2
                                        ((iso u1 u2)P:Prop.P
                                             (pr3
                                                  c
                                                  THead
                                                    Bind b
                                                    u
                                                    THeads (Flat Appl) (lifts (S OO (TApp ts t)) t0
                                                  u2))
          end of h2
          by (tlist_ind_rev . h1 h2 .)
          we proved 
             u:T
               .t0:T
                 .let u1 := THeads (Flat Appl) vs (THead (Bind b) u t0)
                 in c:C
                        .u2:T
                          .pr3 c u1 u2
                            ((iso u1 u2)P:Prop.P
                                 (pr3
                                      c
                                      THead (Bind b) u (THeads (Flat Appl) (lifts (S OO vs) t0)
                                      u2))
       we proved 
          b:B
            .not (eq B b Abst)
              vs:TList
                   .u:T
                     .t0:T
                       .let u1 := THeads (Flat Appl) vs (THead (Bind b) u t0)
                       in c:C
                              .u2:T
                                .pr3 c u1 u2
                                  ((iso u1 u2)P:Prop.P
                                       (pr3
                                            c
                                            THead (Bind b) u (THeads (Flat Appl) (lifts (S OO vs) t0)
                                            u2))