add: new interfaces

interfaces/_legacy/03-func-to-func/main.go

@@ -0,0 +1,82 @@
+// 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"
+	"strings"
+	"unicode"
+)
+
+type filterFunc func(int) bool
+
+func main() {
+	signatures()
+
+	fmt.Println("\n••• WITHOUT FUNC VALUES •••")
+	nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+
+	fmt.Printf("evens      : %d\n", filterEvens(nums...))
+	fmt.Printf("odds       : %d\n", filterOdds(nums...))
+
+	fmt.Println("\n••• FUNC VALUES •••")
+	fmt.Printf("evens      : %d\n", filter(isEven, nums...))
+	fmt.Printf("odds       : %d\n", filter(isOdd, nums...))
+
+	fmt.Println("\n••• MAPPING •••")
+	fmt.Println(strings.Map(unpunct, "hello!!! HOW ARE YOU???? :))"))
+	fmt.Println(strings.Map(unpunct, "TIME IS UP!"))
+}
+
+func unpunct(r rune) rune {
+	if unicode.IsPunct(r) {
+		return -1
+	}
+	return unicode.ToLower(r)
+}
+
+func filter(f filterFunc, nums ...int) (filtered []int) {
+	for _, n := range nums {
+		if f(n) {
+			filtered = append(filtered, n)
+		}
+	}
+	return
+}
+
+func filterOdds(nums ...int) (filtered []int) {
+	for _, n := range nums {
+		if isOdd(n) {
+			filtered = append(filtered, n)
+		}
+	}
+	return
+}
+
+func filterEvens(nums ...int) (filtered []int) {
+	for _, n := range nums {
+		if isEven(n) {
+			filtered = append(filtered, n)
+		}
+	}
+	return
+}
+
+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)
+}