ck

; Comments start with semicolons.

; Clojure is written in "forms", which are just
; lists of things inside parentheses, separated by whitespace.
;
; The clojure reader  assumes that the first thing is a
; function or macro to call, and the rest are arguments.
;
; Here's a function that sets the current namespace:
(ns test)

ck

(ns shades.lenses)

; We only need three fns that know the structure of a lens.
(defn lens [focus fmap] {:focus focus :fmap fmap})
(defn view [x {:keys [focus]}] (focus x))
(defn update [x {:keys [fmap]} f] (fmap f x))

; The identity lens.
(defn fapply [f x] (f x))
(def id (lens identity fapply))