diff Ordinals.agda @ 420:53422a8ea836

bijection
author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Fri, 31 Jul 2020 17:42:25 +0900
parents aa306f5dab9b
children 9984cdd88da3
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--- a/Ordinals.agda	Fri Jul 31 12:57:59 2020 +0900
+++ b/Ordinals.agda	Fri Jul 31 17:42:25 2020 +0900
@@ -313,6 +313,12 @@
         omax<nx {x} {y} {z} x<nz y<nz | tri≈ ¬a refl ¬c = osuc<nx y<nz
         omax<nx {x} {y} {z} x<nz y<nz | tri> ¬a ¬b c = osuc<nx x<nz
 
+        nn<omax : {x nx ny : Ordinal} → x o< next nx → x o< next ny → x o< next (omax nx ny)
+        nn<omax {x} {nx} {ny} xnx xny with trio< nx ny
+        nn<omax {x} {nx} {ny} xnx xny | tri< a ¬b ¬c = subst (λ k → x o< k ) nexto≡ xny
+        nn<omax {x} {nx} {ny} xnx xny | tri≈ ¬a refl ¬c = subst (λ k → x o< k ) nexto≡ xny
+        nn<omax {x} {nx} {ny} xnx xny | tri> ¬a ¬b c = subst (λ k → x o< k ) nexto≡ xnx
+
         record OrdinalSubset (maxordinal : Ordinal) : Set (suc n) where
           field
             os→ : (x : Ordinal) → x o< maxordinal → Ordinal