From c9b6934608ba01a8f7e2dd1ea29a4304c908b3dd Mon Sep 17 00:00:00 2001
From: Greg Brown <greg.brown01@ed.ac.uk>
Date: Tue, 6 Dec 2022 09:08:19 +0000
Subject: Define setoid reindexing.

---
 src/Data/Setoid/Indexed.idr | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Data/Setoid/Indexed.idr b/src/Data/Setoid/Indexed.idr
index 7277932..a04b647 100644
--- a/src/Data/Setoid/Indexed.idr
+++ b/src/Data/Setoid/Indexed.idr
@@ -39,6 +39,10 @@ public export
 (.index) : ISetoid a -> a -> Setoid
 (.index) x i = MkSetoid (x.U i) (x.relation i) (x.equivalence i)
 
+public export
+reindex : (a -> b) -> ISetoid b -> ISetoid a
+reindex f x = MkISetoid (x.U . f) (\i => x.relation $ f i) (\i => x.equivalence $ f i)
+
 public export
 isetoid : (a -> Type) -> ISetoid a
 isetoid u = MkISetoid u (\_ => Equal) (\_ => equiv)
-- 
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