-- | Unsafe indexing.
(!!!) :: (Arity m, Arity n) => Mat m n a -> (Int, Int) -> a
-(!!!) m (i, j) = (row m i) ! j
+(!!!) (Mat rows) (i, j) = (rows ! i) ! j
+
-- | Safe indexing.
-(!!?) :: Mat m n a -> (Int, Int) -> Maybe a
-(!!?) m@(Mat rows) (i, j)
+(!!?) :: (Arity m, Arity n) => Mat m n a -> (Int, Int) -> Maybe a
+(!!?) matrix (i, j)
| i < 0 || j < 0 = Nothing
- | i > V.length rows = Nothing
- | otherwise = if j > V.length (row m j)
- then Nothing
- else Just $ (row m j) ! j
+ | i > (nrows matrix) - 1 = Nothing
+ | j > (ncols matrix) - 1 = Nothing
+ | otherwise = Just $ matrix !!! (i,j)
-- | The number of rows in the matrix.
nrows :: forall m n a. (Arity m) => Mat m n a -> Int
nrows _ = arity (undefined :: m)
+
-- | The number of columns in the first row of the
-- matrix. Implementation stolen from Data.Vector.Fixed.length.
ncols :: forall m n a. (Arity n) => Mat m n a -> Int
ncols _ = arity (undefined :: n)
--- | Return the @i@th row of @m@. Unsafe.
-row :: Mat m n a -> Int -> (Vec n a)
-row (Mat rows) i = rows ! i
-
-
-- | Return the @i@th row of @m@ as a matrix. Unsafe.
-row' :: (Arity m, Arity n) => Mat m n a -> Int -> Row n a
-row' m i =
+row :: (Arity m, Arity n) => Mat m n a -> Int -> Row n a
+row m i =
construct lambda
where
lambda _ j = m !!! (i, j)
--- | Return the @j@th column of @m@. Unsafe.
---column :: Mat m n a -> Int -> (Vec m a)
---column (Mat rows) j =
--- V.map (element j) rows
--- where
--- element = flip (!)
-
-
-- | Return the @j@th column of @m@ as a matrix. Unsafe.
column :: (Arity m, Arity n) => Mat m n a -> Int -> Col m a
column m j =
identity_matrix =
construct (\i j -> if i == j then (fromInteger 1) else (fromInteger 0))
+
-- | Given a positive-definite matrix @m@, computes the
-- upper-triangular matrix @r@ with (transpose r)*r == m and all
-- values on the diagonal of @r@ positive.