let locals in Clojure

Converts tide pool measurements inside a let, then watches a shadowed name snap back.

;; let binds locals in order, so later ones can use earlier ones
(defn pool-report [depth-cm width-cm]
  (let [depth-m (/ depth-cm 100.0)
        width-m (/ width-cm 100.0)
        surface (* width-m width-m)
        volume (* surface depth-m)]
    (str "surface " surface " m2, volume " volume " m3")))

;; a rebinding shadows the outer one only inside its own body
(let [tide "low"]
  (println "outside:" tide)
  (let [tide "high"]
    (println "inside:" tide))
  (println "outside again:" tide))

(println (pool-report 18 60))

How it works

pool-report opens a let where depth-m and width-m scale the centimeter arguments.
surface and volume are bound further down and read those earlier locals.
An inner let rebinds tide for the length of its body, and the outer value returns afterward.

Keywords and builtins used here

defn
let
println
str

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Step 2 of 3 in Values & bindings, step 2 of 27 in Language basics.

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