DEFINITION sty0_gen_cast()
TYPE =
       g:G
         .c:C
           .v1:T
             .t1:T
               .x:T
                 .sty0 g c (THead (Flat Cast) v1 t1) x
                   ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2)
BODY =
        assume gG
        assume cC
        assume v1T
        assume t1T
        assume xT
        suppose Hsty0 g c (THead (Flat Cast) v1 t1) x
           assume yT
           suppose H0sty0 g c y x
             we proceed by induction on H0 to prove 
                eq T y (THead (Flat Cast) v1 t1)
                  ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2)
                case sty0_sort : c0:C n:nat 
                   the thesis becomes 
                   H1:eq T (TSort n) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv2:T.λ:T.sty0 g c0 v1 v2
                       λ:T.λt2:T.sty0 g c0 t1 t2
                       λv2:T.λt2:T.eq T (TSort (next g n)) (THead (Flat Cast) v2 t2)
                      suppose H1eq T (TSort n) (THead (Flat Cast) v1 t1)
                         (H2
                            we proceed by induction on H1 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort True
                                 | TLRef False
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TSort n OF
                                      TSort True
                                    | TLRef False
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TSort n OF
                                            TSort True
                                          | TLRef False
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort True
                                 | TLRef False
                                 | THead   False
                         end of H2
                         consider H2
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Cast) v1 t1 OF
                                TSort True
                              | TLRef False
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (TSort (next g n)) (THead (Flat Cast) v2 t2)
                         we proved 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (TSort (next g n)) (THead (Flat Cast) v2 t2)

                         H1:eq T (TSort n) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g c0 v1 v2
                             λ:T.λt2:T.sty0 g c0 t1 t2
                             λv2:T.λt2:T.eq T (TSort (next g n)) (THead (Flat Cast) v2 t2)
                case sty0_abbr : c0:C d:C v:T i:nat :getl i c0 (CHead d (Bind Abbr) v) w:T :sty0 g d v w 
                   the thesis becomes 
                   H4:eq T (TLRef i) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv2:T.λ:T.sty0 g c0 v1 v2
                       λ:T.λt2:T.sty0 g c0 t1 t2
                       λv2:T.λt2:T.eq T (lift (S i) O w) (THead (Flat Cast) v2 t2)
                   () by induction hypothesis we know 
                      eq T v (THead (Flat Cast) v1 t1)
                        ex3_2 T T λv2:T.λ:T.sty0 g d v1 v2 λ:T.λt2:T.sty0 g d t1 t2 λv2:T.λt2:T.eq T w (THead (Flat Cast) v2 t2)
                      suppose H4eq T (TLRef i) (THead (Flat Cast) v1 t1)
                         (H5
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort False
                                    | TLRef True
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort False
                                          | TLRef True
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Cast) v1 t1 OF
                                TSort False
                              | TLRef True
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (lift (S i) O w) (THead (Flat Cast) v2 t2)
                         we proved 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (lift (S i) O w) (THead (Flat Cast) v2 t2)

                         H4:eq T (TLRef i) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g c0 v1 v2
                             λ:T.λt2:T.sty0 g c0 t1 t2
                             λv2:T.λt2:T.eq T (lift (S i) O w) (THead (Flat Cast) v2 t2)
                case sty0_abst : c0:C d:C v:T i:nat :getl i c0 (CHead d (Bind Abst) v) w:T :sty0 g d v w 
                   the thesis becomes 
                   H4:eq T (TLRef i) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv2:T.λ:T.sty0 g c0 v1 v2
                       λ:T.λt2:T.sty0 g c0 t1 t2
                       λv2:T.λt2:T.eq T (lift (S i) O v) (THead (Flat Cast) v2 t2)
                   () by induction hypothesis we know 
                      eq T v (THead (Flat Cast) v1 t1)
                        ex3_2 T T λv2:T.λ:T.sty0 g d v1 v2 λ:T.λt2:T.sty0 g d t1 t2 λv2:T.λt2:T.eq T w (THead (Flat Cast) v2 t2)
                      suppose H4eq T (TLRef i) (THead (Flat Cast) v1 t1)
                         (H5
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort False
                                    | TLRef True
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort False
                                          | TLRef True
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Cast) v1 t1 OF
                                TSort False
                              | TLRef True
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (lift (S i) O v) (THead (Flat Cast) v2 t2)
                         we proved 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt2:T.sty0 g c0 t1 t2
                              λv2:T.λt2:T.eq T (lift (S i) O v) (THead (Flat Cast) v2 t2)

                         H4:eq T (TLRef i) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g c0 v1 v2
                             λ:T.λt2:T.sty0 g c0 t1 t2
                             λv2:T.λt2:T.eq T (lift (S i) O v) (THead (Flat Cast) v2 t2)
                case sty0_bind : b:B c0:C v:T t0:T t2:T :sty0 g (CHead c0 (Bind b) v) t0 t2 
                   the thesis becomes 
                   H3:eq T (THead (Bind b) v t0) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv2:T.λ:T.sty0 g c0 v1 v2
                       λ:T.λt3:T.sty0 g c0 t1 t3
                       λv2:T.λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Cast) v2 t3)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Flat Cast) v1 t1)
                        (ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g (CHead c0 (Bind b) v) v1 v2
                             λ:T.λt3:T.sty0 g (CHead c0 (Bind b) v) t1 t3
                             λv2:T.λt3:T.eq T t2 (THead (Flat Cast) v2 t3))
                      suppose H3eq T (THead (Bind b) v t0) (THead (Flat Cast) v1 t1)
                         (H4
                            we proceed by induction on H3 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind True | Flat False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Bind b) v t0 OF
                                      TSort False
                                    | TLRef False
                                    | THead k  <λ:K.Prop> CASE k OF Bind True | Flat False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Bind b) v t0 OF
                                            TSort False
                                          | TLRef False
                                          | THead k  <λ:K.Prop> CASE k OF Bind True | Flat False

                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind True | Flat False
                         end of H4
                         consider H4
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Cast) v1 t1 OF
                                TSort False
                              | TLRef False
                              | THead k  <λ:K.Prop> CASE k OF Bind True | Flat False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt3:T.sty0 g c0 t1 t3
                              λv2:T.λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Cast) v2 t3)
                         we proved 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt3:T.sty0 g c0 t1 t3
                              λv2:T.λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Cast) v2 t3)

                         H3:eq T (THead (Bind b) v t0) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g c0 v1 v2
                             λ:T.λt3:T.sty0 g c0 t1 t3
                             λv2:T.λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Cast) v2 t3)
                case sty0_appl : c0:C v:T t0:T t2:T :sty0 g c0 t0 t2 
                   the thesis becomes 
                   H3:eq T (THead (Flat Appl) v t0) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv2:T.λ:T.sty0 g c0 v1 v2
                       λ:T.λt3:T.sty0 g c0 t1 t3
                       λv2:T.λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Cast) v2 t3)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Flat Cast) v1 t1)
                        ex3_2 T T λv2:T.λ:T.sty0 g c0 v1 v2 λ:T.λt3:T.sty0 g c0 t1 t3 λv2:T.λt3:T.eq T t2 (THead (Flat Cast) v2 t3)
                      suppose H3eq T (THead (Flat Appl) v t0) (THead (Flat Cast) v1 t1)
                         (H4
                            we proceed by induction on H3 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef False
                                 | THead k  
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind False
                                         | Flat f<λ:F.Prop> CASE f OF ApplTrue | CastFalse
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Appl) v t0 OF
                                      TSort False
                                    | TLRef False
                                    | THead k  
                                          <λ:K.Prop>
                                            CASE k OF
                                              Bind False
                                            | Flat f<λ:F.Prop> CASE f OF ApplTrue | CastFalse
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Appl) v t0 OF
                                            TSort False
                                          | TLRef False
                                          | THead k  
                                                <λ:K.Prop>
                                                  CASE k OF
                                                    Bind False
                                                  | Flat f<λ:F.Prop> CASE f OF ApplTrue | CastFalse

                               <λ:T.Prop>
                                 CASE THead (Flat Cast) v1 t1 OF
                                   TSort False
                                 | TLRef False
                                 | THead k  
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind False
                                         | Flat f<λ:F.Prop> CASE f OF ApplTrue | CastFalse
                         end of H4
                         consider H4
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Cast) v1 t1 OF
                                TSort False
                              | TLRef False
                              | THead k  
                                    <λ:K.Prop>
                                      CASE k OF
                                        Bind False
                                      | Flat f<λ:F.Prop> CASE f OF ApplTrue | CastFalse
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt3:T.sty0 g c0 t1 t3
                              λv2:T.λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Cast) v2 t3)
                         we proved 
                            ex3_2
                              T
                              T
                              λv2:T.λ:T.sty0 g c0 v1 v2
                              λ:T.λt3:T.sty0 g c0 t1 t3
                              λv2:T.λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Cast) v2 t3)

                         H3:eq T (THead (Flat Appl) v t0) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv2:T.λ:T.sty0 g c0 v1 v2
                             λ:T.λt3:T.sty0 g c0 t1 t3
                             λv2:T.λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Cast) v2 t3)
                case sty0_cast : c0:C v0:T v2:T H1:sty0 g c0 v0 v2 t0:T t2:T H3:sty0 g c0 t0 t2 
                   the thesis becomes 
                   H5:eq T (THead (Flat Cast) v0 t0) (THead (Flat Cast) v1 t1)
                     .ex3_2
                       T
                       T
                       λv3:T.λ:T.sty0 g c0 v1 v3
                       λ:T.λt3:T.sty0 g c0 t1 t3
                       λv3:T.λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v3 t3)
                   (H2) by induction hypothesis we know 
                      eq T v0 (THead (Flat Cast) v1 t1)
                        ex3_2 T T λv3:T.λ:T.sty0 g c0 v1 v3 λ:T.λt2:T.sty0 g c0 t1 t2 λv3:T.λt2:T.eq T v2 (THead (Flat Cast) v3 t2)
                   (H4) by induction hypothesis we know 
                      eq T t0 (THead (Flat Cast) v1 t1)
                        ex3_2 T T λv3:T.λ:T.sty0 g c0 v1 v3 λ:T.λt3:T.sty0 g c0 t1 t3 λv3:T.λt3:T.eq T t2 (THead (Flat Cast) v3 t3)
                      suppose H5eq T (THead (Flat Cast) v0 t0) (THead (Flat Cast) v1 t1)
                         (H6
                            by (f_equal . . . . . H5)
                            we proved 
                               eq
                                 T
                                 <λ:T.T> CASE THead (Flat Cast) v0 t0 OF TSort v0 | TLRef v0 | THead  t t
                                 <λ:T.T> CASE THead (Flat Cast) v1 t1 OF TSort v0 | TLRef v0 | THead  t t

                               eq
                                 T
                                 λe:T.<λ:T.T> CASE e OF TSort v0 | TLRef v0 | THead  t t
                                   THead (Flat Cast) v0 t0
                                 λe:T.<λ:T.T> CASE e OF TSort v0 | TLRef v0 | THead  t t
                                   THead (Flat Cast) v1 t1
                         end of H6
                         (h1
                            (H7
                               by (f_equal . . . . . H5)
                               we proved 
                                  eq
                                    T
                                    <λ:T.T> CASE THead (Flat Cast) v0 t0 OF TSort t0 | TLRef t0 | THead   tt
                                    <λ:T.T> CASE THead (Flat Cast) v1 t1 OF TSort t0 | TLRef t0 | THead   tt

                                  eq
                                    T
                                    λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   tt
                                      THead (Flat Cast) v0 t0
                                    λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   tt
                                      THead (Flat Cast) v1 t1
                            end of H7
                            suppose H8eq T v0 v1
                               (H10
                                  consider H7
                                  we proved 
                                     eq
                                       T
                                       <λ:T.T> CASE THead (Flat Cast) v0 t0 OF TSort t0 | TLRef t0 | THead   tt
                                       <λ:T.T> CASE THead (Flat Cast) v1 t1 OF TSort t0 | TLRef t0 | THead   tt
                                  that is equivalent to eq T t0 t1
                                  we proceed by induction on the previous result to prove sty0 g c0 t1 t2
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H3
sty0 g c0 t1 t2
                               end of H10
                               (H12
                                  we proceed by induction on H8 to prove sty0 g c0 v1 v2
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H1
sty0 g c0 v1 v2
                               end of H12
                               by (refl_equal . .)
                               we proved eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v2 t2)
                               by (ex3_2_intro . . . . . . . H12 H10 previous)
                               we proved 
                                  ex3_2
                                    T
                                    T
                                    λv3:T.λ:T.sty0 g c0 v1 v3
                                    λ:T.λt3:T.sty0 g c0 t1 t3
                                    λv3:T.λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v3 t3)

                               eq T v0 v1
                                 (ex3_2
                                      T
                                      T
                                      λv3:T.λ:T.sty0 g c0 v1 v3
                                      λ:T.λt3:T.sty0 g c0 t1 t3
                                      λv3:T.λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v3 t3))
                         end of h1
                         (h2
                            consider H6
                            we proved 
                               eq
                                 T
                                 <λ:T.T> CASE THead (Flat Cast) v0 t0 OF TSort v0 | TLRef v0 | THead  t t
                                 <λ:T.T> CASE THead (Flat Cast) v1 t1 OF TSort v0 | TLRef v0 | THead  t t
eq T v0 v1
                         end of h2
                         by (h1 h2)
                         we proved 
                            ex3_2
                              T
                              T
                              λv3:T.λ:T.sty0 g c0 v1 v3
                              λ:T.λt3:T.sty0 g c0 t1 t3
                              λv3:T.λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v3 t3)

                         H5:eq T (THead (Flat Cast) v0 t0) (THead (Flat Cast) v1 t1)
                           .ex3_2
                             T
                             T
                             λv3:T.λ:T.sty0 g c0 v1 v3
                             λ:T.λt3:T.sty0 g c0 t1 t3
                             λv3:T.λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Cast) v3 t3)
             we proved 
                eq T y (THead (Flat Cast) v1 t1)
                  ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2)
          we proved 
             y:T
               .sty0 g c y x
                 (eq T y (THead (Flat Cast) v1 t1)
                      ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2))
          by (insert_eq . . . . previous H)
          we proved ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2)
       we proved 
          g:G
            .c:C
              .v1:T
                .t1:T
                  .x:T
                    .sty0 g c (THead (Flat Cast) v1 t1) x
                      ex3_2 T T λv2:T.λ:T.sty0 g c v1 v2 λ:T.λt2:T.sty0 g c t1 t2 λv2:T.λt2:T.eq T x (THead (Flat Cast) v2 t2)