From 5a53c75f533f2ae758635e1989c4e7fb2b6469d5 Mon Sep 17 00:00:00 2001
From: Chloe Brown <chloe.brown.00@outlook.com>
Date: Sun, 16 Apr 2023 14:50:55 +0100
Subject: Prove whnfs do not reduce.

---
 src/Core/Reduction.idr | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

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

diff --git a/src/Core/Reduction.idr b/src/Core/Reduction.idr
index 7516648..9015d14 100644
--- a/src/Core/Reduction.idr
+++ b/src/Core/Reduction.idr
@@ -3,6 +3,7 @@ module Core.Reduction
 import Core.Environment
 import Core.Declarative
 import Core.Term
+import Core.Term.NormalForm
 import Core.Term.Substitution
 import Core.Term.Thinned
 import Core.Thinning
@@ -131,3 +132,25 @@ termStepImpliesSubjectWf (ConvStep step tyConv) = ConvWf (termStepImpliesSubject
 export
 typeStepImpliesSubjectWf : TypeStep env a b -> TypeWf env a
 typeStepImpliesSubjectWf = LiftWf . termStepImpliesSubjectWf
+
+-- Whnfs Do Not Reduce ---------------------------------------------------------
+
+export
+whnfNoTermStep : Whnf t -> Not (TermStep env t u a)
+whnfNoTermStep (Ntrl (App n)) (AppStep step tmWf) = whnfNoTermStep (Ntrl n) step
+whnfNoTermStep (Ntrl (App n)) (PiBeta tyWf tmWf tmWf1) impossible
+whnfNoTermStep n (ConvStep step tyConv) = whnfNoTermStep n step
+
+export
+whnfNoTypeStep : Whnf a -> Not (TypeStep env a b)
+whnfNoTypeStep = whnfNoTermStep
+
+export
+whnfTypeRedStays : Whnf a -> TypeReduce env a b -> a = b
+whnfTypeRedStays n (Refl tyWf) = Refl
+whnfTypeRedStays n (Step step steps) = absurd (whnfNoTypeStep n step)
+
+export
+whnfTermRedStays : Whnf t -> TermReduce env t u a -> t = u
+whnfTermRedStays n (Refl tmWf) = Refl
+whnfTermRedStays n (Step step steps) = absurd (whnfNoTermStep n step)
-- 
cgit v1.2.3