defn basics in Clojure

Defines a baker's hydration percentage with a docstring and a private helper.

;; the string after the name is a docstring, stored on the var
(defn hydration
  "Water as a percent of flour weight, rounded to a whole number."
  [flour-g water-g]
  (Math/round (* 100.0 (/ water-g flour-g))))

;; defn- keeps a helper private to this namespace
(defn- describe [pct]
  (cond
    (< pct 65) "stiff"
    (< pct 80) "standard"
    :else "slack"))

(def dough (hydration 500 375))
(println "hydration" dough "-" (describe dough))
(println (:doc (meta #'hydration)))

How it works

1. hydration takes [flour-g water-g] after its docstring and rounds the percentage.
2. defn- makes describe private to the namespace, where cond names three ranges.
3. (:doc (meta #'hydration)) reads the docstring back off the var at the end.

Keywords and builtins used here

• cond
• def
• defn
• describe
• hydration
• meta
• println

The run, in numbers

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16

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459

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Three-star pace

80 tpm

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Type this snippet

Step 1 of 3 in Functions, step 7 of 27 in Language basics.

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