015 - Double down

A chance to use the function definitions we learnt in exercise #14

src/four_clojure/015_double_down.clj

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+(ns four-clojure.015-double-down)
+
+;; #015 Double down
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Solutions
+;; Difficulty:	Elementary
+;; Topics:
+
+;; Write a function which doubles a number.
+
+;; (= (__ 2) 4)
+;; (= (__ 3) 6)
+;; (= (__ 11) 22)
+;; (= (__ 7) 14)
+
+
+;; Deconstruct the problem
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; A chance to use the function definitions we have just learnt
+
+;; we need to write a function that takes a single argument
+
+(fn [arg])
+
+;; The behaviour of the function is to double the value of the argument,
+;; so we can do this by multiplying by 2
+
+(fn [arg]
+  (* arg 2))
+
+;; Now we can call this definition with the 4Clojure tests
+
+((fn [arg]
+   (* arg 2))
+ 2)
+;; => 4
+
+;; and this works for all the tests.
+
+;; we can also write the function definition using the short form
+#(* % 2)
+
+;; and call the short form with the same test data
+(#(* % 2) 2)
+;; => 4
+
+
+;; Answers summary
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Normal function definition
+(fn [arg]
+  (* arg 2))
+
+;; short form function definition
+#(* % 2)