Document that mshapeTree is partialmild-tweaks-repackaged

1 files changed, 4 insertions, 0 deletions

diff --git a/src/Data/Array/Nested/Mixed.hs b/src/Data/Array/Nested/Mixed.hs
index eb05eaa..f9d9aa8 100644
--- a/src/Data/Array/Nested/Mixed.hs
+++ b/src/Data/Array/Nested/Mixed.hs
@@ -355,6 +355,9 @@ class Elt a where
   -- | Tree giving the shape of every array component.
   type ShapeTree a
 
+  -- | Produces an internal representation of a tree of shapes of (potentially)
+  -- nested arrays. If the argument is an array, it requires that the array
+  -- is not empty (it's guaranteed to crash early otherwise).
   mshapeTree :: a -> ShapeTree a
 
   mshapeTreeEq :: Proxy a -> ShapeTree a -> ShapeTree a -> Bool
@@ -676,6 +679,7 @@ instance Elt a => Elt (Mixed sh' a) where
 
   type ShapeTree (Mixed sh' a) = (IShX sh', ShapeTree a)
 
+  -- This requires that @arr@ is not empty.
   mshapeTree :: Mixed sh' a -> ShapeTree (Mixed sh' a)
   mshapeTree arr = (mshape arr, mshapeTree (mindex arr (ixxZero (ssxFromShX (mshape arr)))))