update: directory structure

advfuncs/05-higher-order-funcs/main.go

@@ -0,0 +1,58 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+)
+
+type filterFunc func(int) bool
+
+func main() {
+	fmt.Println("••• HIGHER-ORDER FUNCS •••")
+
+	nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+
+	odd := reverse(reverse(isEven))
+	fmt.Printf("reversed   : %t\n", odd(8))
+
+	fmt.Printf("> 3        : %d\n", filter(greater(3), nums...))
+	fmt.Printf("> 6        : %d\n", filter(greater(6), nums...))
+	fmt.Printf("<= 6       : %d\n", filter(lesseq(6), nums...))
+	fmt.Printf("<= 6       : %d\n", filter(reverse(greater(6)), nums...))
+}
+
+func reverse(f filterFunc) filterFunc {
+	return func(n int) bool {
+		return !f(n)
+	}
+}
+
+func greater(min int) filterFunc {
+	return func(n int) bool {
+		return n > min
+	}
+}
+
+func lesseq(max int) filterFunc {
+	return func(n int) bool {
+		return n <= max
+	}
+}
+
+func filter(f filterFunc, nums ...int) (filtered []int) {
+	for _, n := range nums {
+		if f(n) {
+			filtered = append(filtered, n)
+		}
+	}
+	return
+}
+
+func isEven(n int) bool { return n%2 == 0 }
+func isOdd(m int) bool  { return m%2 == 1 }