move: advanced funcs to functional programming

27-functional-programming/_legacy/02-func-values/main.go

@@ -0,0 +1,52 @@
+// 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() {
+	signatures()
+	funcValues()
+}
+
+func isEven(n int) bool {
+	return n%2 == 0
+}
+
+func isOdd(m int) bool {
+	return m%2 == 1
+}
+
+func signatures() {
+	fmt.Println("••• FUNC SIGNATURES (TYPES) •••")
+	fmt.Printf("isEven     : %T\n", isEven)
+	fmt.Printf("isOdd      : %T\n", isOdd)
+}
+
+func funcValues() {
+	fmt.Println("\n••• FUNC VALUES (VARS) •••")
+
+	// var value func(int) bool
+	var value filterFunc
+	fmt.Printf("value nil? : %t\n", value == nil)
+
+	value = isEven
+	fmt.Printf("value(2)   : %t\n", value(2))
+	fmt.Printf("isEven(2)  : %t\n", isEven(2))
+
+	value = isOdd
+	fmt.Printf("value(1)   : %t\n", value(1))
+	fmt.Printf("isOdd(1)   : %t\n", isOdd(1))
+
+	fmt.Printf("value nil? : %t\n", value == nil)
+	fmt.Printf("value      : %p\n", value)
+	fmt.Printf("isEven     : %p\n", isEven)
+	fmt.Printf("isOdd      : %p\n", isOdd)
+}