add declared-a-function eg

Author: hegdeashwin

codes/ch2_functions/declared-a-function.go

@@ -0,0 +1,72 @@
+package main
+
+import "fmt"
+
+/**
+ * User defined type Profile act as struct type
+ */
+type Profile struct {
+	name string
+	username string
+	message string
+}
+
+type Printer func(string) ()
+/**
+ * Define a CreateMessage function;
+ * 
+ * username is variadic function, can only use ... as final argument in list
+ */
+func CreateMessage(name string, username string, message ...string) (welcome string, info string) {
+
+	/**
+	 * <naming-return-val1> = string
+	 * <naming-return-val2> = string
+	 */
+	welcome = "\n" + message[0] + " " + name
+	info = "You are authorize to access the system: " + username + "\n"
+
+	fmt.Println(message[1])
+	fmt.Println(message[2])
+	fmt.Println("Number of parameters: ", len(message))
+
+	return
+}
+
+func Print(s string) {
+	fmt.Print(s)
+}
+
+func PrintLine(s string) {
+	fmt.Println(s)
+}
+
+/**
+ * Define a Greeting function;
+ */
+func Greeting(github Profile, do Printer) {
+	
+	wel, inf := CreateMessage(github.name, github.username, github.message, "Go is concurrent", "Go is awesome")
+
+	/**
+	 * Commenting exact below "Println(wel) line would throw an error "wel declared and not used"
+	 * In case you want to ignore the wel declaration and use info => replace wel with _ as below syntax
+	 *
+	 * E.g. _, info := CreateMessage(github.name, github.username, github.message)
+	 */
+	do(wel)
+	do(inf)
+
+	// fmt.Println(_)  // Cannot use _ as value
+}
+
+func main() {
+
+	var github = Profile{"Ashwin Hegde", "hegdeashwin", "Welcome to Go world!"}
+
+	/**
+	 * Call the function and pass the data to the function
+	 */
+	Greeting(github, Print) 
+	Greeting(github, PrintLine)
+}