include "ground/relocation/tr_uni_pap.ma".
include "ground/relocation/tr_compose_pap.ma".
include "ground/relocation/tr_pap_eq.ma".
+include "ground/relocation/tr_pap_hdtl_eq.ma".
include "ground/notation/functions/atsection_2.ma".
include "ground/arith/nat_lt.ma".
-include "ground/arith/nat_plus_rplus.ma".
+include "ground/arith/nat_plus_pplus.ma".
include "ground/arith/nat_pred_succ.ma".
lemma nlt_npsucc_bi (n1) (n2):
<tr_nap_unfold <tr_nap_unfold
/3 width=1 by tr_pap_eq_repl, eq_f/
qed.
+
+lemma tr_eq_inv_nap_zero_tl_bi (f1) (f2):
+ f1@§❨𝟎❩ = f2@§❨𝟎❩ → ⇂f1 ≗ ⇂f2 → f1 ≗ f2.
+#f1 #f2
+<tr_nap_unfold <tr_nap_unfold #H1 #H2
+/3 width=1 by tr_eq_inv_pap_unit_tl_bi, eq_inv_pnpred_bi/
+qed-.
+
+lemma tr_nap_plus_sn (f) (m) (n):
+ (⫯⇂*[↑n]f)@§❨m❩+f@§❨n❩ = f@§❨m+n❩.
+#f #m @(nat_ind_succ … m) -m [| #m #_ ] #n
+[ <nplus_zero_sn <nplus_zero_sn //
+| <tr_nap_push <nplus_comm in ⊢ (???%);
+ <tr_nap_unfold <tr_nap_unfold <tr_nap_unfold
+ <nsucc_pnpred <nrplus_inj_sn <nrplus_pnpred_dx
+ >nrplus_npsucc_sn <nrplus_inj_dx
+ <pplus_comm in ⊢ (???%); <tr_pap_plus //
+]
+qed.
+
+lemma tr_nap_plus_dx (f) (m) (n):
+ ⇂*[n]f@§❨m❩+(⫯f)@§❨n❩ = f@§❨m+n❩.
+#f #m #n @(nat_ind_succ … n) -n [| #n #_ ]
+[ //
+| <tr_nap_push
+ <tr_nap_unfold <tr_nap_unfold <tr_nap_unfold
+ <nsucc_pnpred <nplus_pnpred_sn
+ >nrplus_npsucc_sn <nrplus_inj_dx
+ <tr_pap_plus //
+]
+qed.