Add comments to everything

src/Data/NumIdr/Array/Order.idr

@@ -6,9 +6,21 @@ import Data.Permutation
 %default total
 
 
+||| An order is an abstract representation of the way in which array
+||| elements are stored in memory. Orders are used to calculate strides,
+||| which provide a method of converting an array coordinate into a linear
+||| memory location.
+|||
+||| @ rk The rank of the array this order applies to
 public export
 data Order : (rk : Nat) -> Type where
+
+  ||| C-like order, or contiguous order. This order stores elements in a
+  ||| row-major fashion (the last axis is the least significant).
   COrder : Order rk
+
+  ||| Fortran-like order. This order stores elements in a column-major
+  ||| fashion (the first axis is the least significant).
   FOrder : Order rk
 
 
@@ -24,7 +36,9 @@ scanr f q0 (x::xs) = f x (head qs) :: qs
   where qs : Vect len res
         qs = scanr f q0 xs
 
+||| Calculate an array's strides given its order and shape.
 export
 calcStrides : Order rk -> Vect rk Nat -> Vect rk Nat
-calcStrides COrder v = tail $ scanr (*) 1 v
-calcStrides FOrder v = init $ scanl (*) 1 v
+calcStrides _      []        = []
+calcStrides COrder v@(_::_)  = scanr (*) 1 $ tail v
+calcStrides FOrder v@(_::_)  = scanl (*) 1 $ init v