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(.require
[library
[lux (.except)
[abstract
[functor (.only Functor)]
comonad]
[type
implicit]]])
(type .public (Store s a)
(Record
[#cursor s
#peek (-> s a)]))
(def (extend f wa)
(All (_ s a b) (-> (-> (Store s a) b) (Store s a) (Store s b)))
[#cursor (the #cursor wa)
#peek (function (_ s) (f (has #cursor s wa)))])
(def .public functor
(All (_ s) (Functor (Store s)))
(implementation
(def (each f fa)
(extend (function (_ store)
(f (at store peek (at store cursor))))
fa))))
(def .public comonad
(All (_ s) (CoMonad (Store s)))
(implementation
(def functor
..functor)
(def (out wa)
(a/an peek (a/an cursor)))
(def disjoint
(extend id))))
(def .public (peeks trans store)
(All (_ s a) (-> (-> s s) (Store s a) a))
(|> (a/an cursor) trans (a/an peek)))
(def .public (seek cursor store)
(All (_ s a) (-> s (Store s a) (Store s a)))
(at (a/an disjoint store) peek cursor))
(def .public (seeks change store)
(All (_ s a) (-> (-> s s) (Store s a) (Store s a)))
(|> store (a/an disjoint) (peeks change)))
(def .public (experiment Functor<f> change store)
(All (_ f s a) (-> (Functor f) (-> s (f s)) (Store s a) (f a)))
(at Functor<f> each (a/an peek) (change (a/an cursor))))
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