migration

clojure/examples/1_5_functions-2.clj

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+(chapter "High-order Functions")
+
+(section "Ordinary functions")
+(example "Identity function"
+         (identity [1 2 3]))
+(example "Constant function"
+         ((constantly 10) 20 30))
+
+(section "High-order functions")
+(example "Function composition"
+         ((comp square square square) 2)
+         ((comp #(* % 2) #(+ % 2)) 10))
+(example "Currying"
+         (def sum (partial foldLeft' 0 +))
+         (sum [1 2 3]))
+(example "Reduce"
+         (def sum' (partial reduce + 0))
+         (sum' [1 2 3]))
+(example "Application"
+         (apply + [1 2 3]))
+(example "Map"
+         (mapv inc (range 10)))
+(example "Juxtaposition"
+         ((juxt + - * /) 1 2 3 4))
+
+(section "Variable-argument functions")
+(example "Sum of squares"
+         (defn sumSquares [& xs] (apply + (map square xs)))
+         (sumSquares 3 4))
+(example "Sum of squares (anonymous)"
+         (#(apply + (map square %&)) 3 4))
+
+(example "Explicit multi-arity"
+         (defn countArgs
+           ([] "zero")
+           ([a] "one")
+           ([a b] "two")
+           ([a b & as] (str (+ 2 (count as)))))
+         (countArgs)
+         (countArgs 1)
+         (countArgs 1 2)
+         (countArgs 1 2 3))