Data.Vec.Pull.Lens

Indexing

ix :: Fin n -> Lens' (Vec n a) a

Index lens.

>>> ('a' L.::: 'b' L.::: 'c' L.::: L.VNil) ^. L._Pull . ix (FS FZ)
'b'

>>> ('a' L.::: 'b' L.::: 'c' L.::: L.VNil) & L._Pull . ix (FS FZ) .~ 'x'
'a' ::: 'x' ::: 'c' ::: VNil

_Cons :: Iso (Vec ('S n) a) (Vec ('S n) b) (a, Vec n a) (b, Vec n b)

Match on non-empty Vec.

Note: lens _Cons is a ReifiedPrism. In fact, Vec n a cannot have an instance of Cons as types don't match.

_head :: Lens' (Vec ('S n) a) a

Head lens. Note: lens _head is a Traversal'.

>>> ('a' L.::: 'b' L.::: 'c' L.::: L.VNil) ^. L._Pull . _head
'a'

>>> ('a' L.::: 'b' L.::: 'c' L.::: L.VNil) & L._Pull . _head .~ 'x'
'x' ::: 'b' ::: 'c' ::: VNil

_tail :: Lens' (Vec ('S n) a) (Vec n a)

Head lens. Note: lens _head is a Traversal'.

Conversions

_Vec :: SNatI n => Prism' [a] (Vec n a)

Prism from list.