From c6b912051ddac25c9d7efe2f8162eac9068a335c Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Thu, 13 Jun 2024 13:09:17 +0200
Subject: Add KnownShape generators from ShS

---
 src/Data/Array/Nested/Internal/Shape.hs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/Data/Array/Nested/Internal/Shape.hs b/src/Data/Array/Nested/Internal/Shape.hs
index 4fa4284..f449536 100644
--- a/src/Data/Array/Nested/Internal/Shape.hs
+++ b/src/Data/Array/Nested/Internal/Shape.hs
@@ -25,6 +25,7 @@
 {-# OPTIONS_GHC -fplugin GHC.TypeLits.KnownNat.Solver #-}
 module Data.Array.Nested.Internal.Shape where
 
+import Data.Array.Shape qualified as O
 import Data.Array.Mixed.Types
 import Data.Coerce (coerce)
 import Data.Foldable qualified as Foldable
@@ -237,6 +238,9 @@ shrTail (ShR list) = ShR (listrTail list)
 shrAppend :: forall n m i. ShR n i -> ShR m i -> ShR (n + m) i
 shrAppend = coerce (listrAppend @_ @i)
 
+-- | This function can also be used to conjure up a 'KnownNat' dictionary;
+-- pattern matching on the returned 'SNat' with the 'pattern SNat' pattern
+-- synonym yields 'KnownNat' evidence.
 shrRank :: ShR n i -> SNat n
 shrRank (ShR sh) = listrRank sh
 
@@ -492,6 +496,14 @@ class KnownShS sh where knownShS :: ShS sh
 instance KnownShS '[] where knownShS = ZSS
 instance (KnownNat n, KnownShS sh) => KnownShS (n : sh) where knownShS = natSing :$$ knownShS
 
+shsKnownShS :: ShS sh -> Dict KnownShS sh
+shsKnownShS ZSS = Dict
+shsKnownShS (SNat :$$ sh) | Dict <- shsKnownShS sh = Dict
+
+shsOrthotopeShape :: ShS sh -> Dict O.Shape sh
+shsOrthotopeShape ZSS = Dict
+shsOrthotopeShape (SNat :$$ sh) | Dict <- shsOrthotopeShape sh = Dict
+
 
 -- | Untyped: length is checked at runtime.
 instance KnownShS sh => IsList (ListS sh (Const i)) where
-- 
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