From 3eb03e2347b35432f7eae7d6847ec9ecf1dff19e Mon Sep 17 00:00:00 2001
From: Chloe Brown <chloe.brown.00@outlook.com>
Date: Thu, 1 Jun 2023 11:54:49 +0100
Subject: Define terms with substitution as an operation.

---
 src/Total/Reduction.idr | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 src/Total/Reduction.idr

(limited to 'src/Total/Reduction.idr')

diff --git a/src/Total/Reduction.idr b/src/Total/Reduction.idr
new file mode 100644
index 0000000..efa6f74
--- /dev/null
+++ b/src/Total/Reduction.idr
@@ -0,0 +1,65 @@
+module Total.Reduction
+
+import Total.Term
+
+public export
+data (>) : Term ctx ty -> Term ctx ty -> Type where
+  AbsCong : t > u -> Abs t > Abs u
+  AppCong1 : t > u -> App t v > App u v
+  AppCong2 : u > v -> App t u > App t v
+  AppBeta : App (Abs t) u > subst t (Base Id :< u)
+  SucCong : t > u -> Suc t > Suc u
+  RecCong1 : t1 > t2 -> Rec t1 u v > Rec t2 u v
+  RecCong2 : u1 > u2 -> Rec t u1 v > Rec t u2 v
+  RecCong3 : v1 > v2 -> Rec t u v1 > Rec t u v2
+  RecZero : Rec Zero u v > u
+  RecSuc : Rec (Suc t) u v > App v (Rec t u v)
+
+%name Reduction.(>) step
+
+public export
+data (>=) : Term ctx ty -> Term ctx ty -> Type where
+  Lin : t >= t
+  (:<) : t >= u -> u > v -> t >= v
+
+%name Reduction.(>=) steps
+
+export
+(++) : t >= u -> u >= v -> t >= v
+steps ++ [<] = steps
+steps ++ steps' :< step = (steps ++ steps') :< step
+
+export
+AbsCong' : t >= u -> Abs t >= Abs u
+AbsCong' [<] = [<]
+AbsCong' (steps :< step) = AbsCong' steps :< AbsCong step
+
+export
+AppCong1' : t >= u -> App t v >= App u v
+AppCong1' [<] = [<]
+AppCong1' (steps :< step) = AppCong1' steps :< AppCong1 step
+
+export
+AppCong2' : u >= v -> App t u >= App t v
+AppCong2' [<] = [<]
+AppCong2' (steps :< step) = AppCong2' steps :< AppCong2 step
+
+export
+SucCong' : t >= u -> Suc t >= Suc u
+SucCong' [<] = [<]
+SucCong' (steps :< step) = SucCong' steps :< SucCong step
+
+export
+RecCong1' : t1 >= t2 -> Rec t1 u v >= Rec t2 u v
+RecCong1' [<] = [<]
+RecCong1' (steps :< step) = RecCong1' steps :< RecCong1 step
+
+export
+RecCong2' : u1 >= u2 -> Rec t u1 v >= Rec t u2 v
+RecCong2' [<] = [<]
+RecCong2' (steps :< step) = RecCong2' steps :< RecCong2 step
+
+export
+RecCong3' : v1 >= v2 -> Rec t u v1 >= Rec t u v2
+RecCong3' [<] = [<]
+RecCong3' (steps :< step) = RecCong3' steps :< RecCong3 step
-- 
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