More shape/index conversion functions

1 files changed, 17 insertions, 0 deletions

diff --git a/src/Data/Array/Nested/Shaped/Shape.hs b/src/Data/Array/Nested/Shaped/Shape.hs
index d34f3ec..ab16422 100644
--- a/src/Data/Array/Nested/Shaped/Shape.hs
+++ b/src/Data/Array/Nested/Shaped/Shape.hs
@@ -248,6 +248,12 @@ ixsInit (IxS list) = IxS (listsInit list)
 ixsLast :: IxS (n : sh) i -> i
 ixsLast (IxS list) = getConst (listsLast list)
 
+-- TODO: this takes a ShS because there are KnownNats inside IxS.
+ixsCast :: ShS sh' -> IxS sh i -> IxS sh' i
+ixsCast ZSS ZIS = ZIS
+ixsCast (_ :$$ sh) (i :.$ idx) = i :.$ ixsCast sh idx
+ixsCast _ _ = error "ixsCast: ranks don't match"
+
 ixsAppend :: forall sh sh' i. IxS sh i -> IxS sh' i -> IxS (sh ++ sh') i
 ixsAppend = coerce (listsAppend @_ @(Const i))
 
@@ -374,6 +380,17 @@ shsOrthotopeShape :: ShS sh -> Dict O.Shape sh
 shsOrthotopeShape ZSS = Dict
 shsOrthotopeShape (SNat :$$ sh) | Dict <- shsOrthotopeShape sh = Dict
 
+-- | This function is a hack made possible by the 'KnownNat' inside 'ListS'.
+-- This function may be removed in a future release.
+shsFromListS :: ListS sh f -> ShS sh
+shsFromListS ZS = ZSS
+shsFromListS (_ ::$ l) = SNat :$$ shsFromListS l
+
+-- | This function is a hack made possible by the 'KnownNat' inside 'IxS'. This
+-- function may be removed in a future release.
+shsFromIxS :: IxS sh i -> ShS sh
+shsFromIxS (IxS l) = shsFromListS l
+
 
 -- | Untyped: length is checked at runtime.
 instance KnownShS sh => IsList (ListS sh (Const i)) where