(* Note: this is Tait's iii, or Girard's CR4 *)
definition S2 ≝ λRR:relation4 genv lenv term term. λRS:relation term. λRP,C:candidate.
∀G,L,Vs. all … (RP G L) Vs →
- ∀T. 𝐒⦃T⦄ → NF … (RR G L) RS T → C G L (ⒶVs.T).
+ ∀T. 𝐒⦃T⦄ → nf RR RS G L T → C G L (ⒶVs.T).
(* Note: this generalizes Tait's ii *)
definition S3 ≝ λC:candidate.
∀a,G,L,Vs,V,T,W.
C G L (ⒶVs.ⓓ{a}ⓝW.V.T) → C G L (ⒶVs.ⓐV.ⓛ{a}W.T).
-definition S4 ≝ λRP,C:candidate.
- ∀G,L,Vs. all … (RP G L) Vs → ∀s. C G L (ⒶVs.⋆s).
-
definition S5 ≝ λC:candidate. ∀I,G,L,K,Vs,V1,V2,i.
C G L (ⒶVs.V2) → ⬆*[↑i] V1 ≘ V2 →
⬇*[i] L ≘ K.ⓑ{I}V1 → C G L (ⒶVs.#i).
{ s1: S1 RP C;
s2: S2 RR RS RP C;
s3: S3 C;
- s4: S4 RP C;
s5: S5 C;
s6: S6 RP C;
s7: S7 C
(* Basic_1: was:
sc3_sn3 sc3_abst sc3_appl sc3_abbr sc3_bind sc3_cast
*)
+(* Note: one sort must exist *)
lemma acr_gcr: ∀RR,RS,RP. gcp RR RS RP → gcr RR RS RP RP →
∀A. gcr RR RS RP (acr RP A).
#RR #RS #RP #H1RP #H2RP #A elim A -A //
#B #A #IHB #IHA @mk_gcr
[ #G #L #T #H
- elim (cp1 … H1RP G L) #s #HK
+ letin s ≝ 0 (* one sort must exist *)
+ lapply (cp1 … H1RP G L s) #HK
lapply (s2 … IHB G L (Ⓔ) … HK) // #HB
lapply (H (𝐈𝐝) L (⋆s) T ? ? ?) -H
/3 width=6 by s1, cp3, drops_refl, lifts_refl/
elim (lifts_inv_flat1 … H0) -H0 #U0 #X #HU0 #HX #H destruct
elim (lifts_inv_bind1 … HX) -HX #W0 #T0 #HW0 #HT0 #H destruct
@(s3 … IHA … (V0⨮V0s)) /5 width=6 by lifts_applv, lifts_flat, lifts_bind/
-| #G #L #Vs #HVs #s #f #L0 #V0 #X #HL0 #H #HB
- elim (lifts_inv_applv1 … H) -H #V0s #X0 #HV0s #H0 #H destruct
- >(lifts_inv_sort1 … H0) -X0
- lapply (s1 … IHB … HB) #HV0
- @(s4 … IHA … (V0⨮V0s)) /3 width=7 by gcp2_all, conj/
| #I #G #L #K #Vs #V1 #V2 #i #HA #HV12 #HLK #f #L0 #V0 #X #HL0 #H #HB
elim (lifts_inv_applv1 … H) -H #V0s #X0 #HV0s #H0 #H destruct
elim (lifts_inv_lref1 … H0) -H0 #j #Hf #H destruct