Add next code of chapter 4

chapter_04/activity_4.02/main.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+  "fmt"
+  "os"
+)
+
+func getPassedArgs() string {
+
+  if len(os.Args) != 2 {
+    fmt.Printf("Exactly 1 argument is needed\n")
+    os.Exit(1)
+  }
+
+  return os.Args[1]
+
+}
+
+func main() {
+
+  m := map[string]string{
+    "305": "Sue",
+    "204": "Bob",
+    "631": "Jake",
+    "073": "Tracy",
+  }
+
+  key := getPassedArgs()
+  if name := m[key]; name != "" {
+    fmt.Println("Hi,", name)
+  } else {
+    fmt.Println(key, "not found")
+    os.Exit(1)
+  }
+
+}

chapter_04/activity_4.03/main.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+  "fmt"
+  "os"
+  "strings"
+)
+
+type locale struct {
+  language string
+  region   string
+}
+
+func getLocales() map[locale]struct{} {
+
+  supportedLocales := make(map[locale]struct{}, 5)
+  supportedLocales[locale{"en", "US"}] = struct{}{}
+  supportedLocales[locale{"en", "CN"}] = struct{}{}
+  supportedLocales[locale{"fr", "CN"}] = struct{}{}
+  supportedLocales[locale{"fr", "FR"}] = struct{}{}
+  supportedLocales[locale{"ru", "RU"}] = struct{}{}
+  return supportedLocales
+
+}
+
+func localExists(l locale) bool {
+
+  _, exists := getLocales()[l]
+  return exists
+
+}
+
+func main() {
+
+  if len(os.Args) != 2 {
+    fmt.Println("No locale passed")
+    os.Exit(1)
+  }
+
+  localeParts := strings.Split(os.Args[1], "_")
+  if len(localeParts) != 2 {
+    fmt.Printf("Invalid locale passed: %v\n", os.Args[1])
+    os.Exit(1)
+  }
+
+  passedLocale := locale{
+    language: localeParts[0],
+    region:   localeParts[1],
+  }
+
+  if !localExists(passedLocale) {
+    fmt.Printf("Locale not supported: %v\n", os.Args[1])
+    os.Exit(1)
+  }
+  fmt.Println("Locale passed is supported")
+
+}

chapter_04/exercise_4.08/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+  "fmt"
+  "os"
+)
+
+func getPassedArgs(minArgs int) []string {
+
+  if len(os.Args) < minArgs {
+    fmt.Printf("At least %v arguments are needed\n", minArgs)
+    os.Exit(1)
+  }
+
+  var args []string
+  for i := 1; i < len(os.Args); i++ {
+    args = append(args, os.Args[i])
+  }
+
+  return args
+
+}
+
+func findLongest(args []string) string {
+
+  var longest string
+  for i := 0; i < len(args); i++ {
+    if len(args[i]) > len(longest) {
+      longest = args[i]
+    }
+  }
+
+  return longest
+
+}
+
+func main() {
+
+  if longest := findLongest(getPassedArgs(3)); len(longest) > 0 {
+    fmt.Println("The longest word passed was:", longest)
+  } else {
+    fmt.Println("There was an error")
+    os.Exit(1)
+  }
+
+}

chapter_04/exercise_4.09/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+  "fmt"
+  "os"
+)
+
+func getPassedArgs() []string {
+
+  var args []string
+  for i := 1; i < len(os.Args); i++ {
+    args = append(args, os.Args[i])
+  }
+
+  return args
+
+}
+
+func getLocals(extraLocals []string) []string {
+
+  var locales []string
+  locales = append(locales, "en_US", "fr_FR")
+  locales = append(locales, extraLocals...)
+  return locales
+
+}
+
+func main() {
+
+  locales := getLocals(getPassedArgs())
+  fmt.Println("Locales to use:", locales)
+
+}

chapter_04/exercise_4.10/main.go

@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func message() string {
+
+  s := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+  m := fmt.Sprintln("First:   ", s[0], s[0:1], s[:1])
+  m += fmt.Sprintln("Last:    ", s[len(s)-1], s[len(s)-1:len(s)], s[len(s)-1:])
+  m += fmt.Sprintln("First 5: ", s[:5])
+  m += fmt.Sprintln("Last 4:  ", s[len(s)-4:])
+  m += fmt.Sprintln("Middle 5:", s[2:7])
+  return m
+
+}
+
+func main() {
+
+  fmt.Print(message())
+
+}

chapter_04/exercise_4.11/main.go

@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func genSlices() ([]int, []int, []int) {
+
+  var s1 []int
+  s2 := make([]int, 10)
+  s3 := make([]int, 10, 50)
+  return s1, s2, s3
+
+}
+
+func main() {
+
+  s1, s2, s3 := genSlices()
+  fmt.Printf("s1: len = %v cap = %v\n", len(s1), cap(s1))
+  fmt.Printf("s2: len = %v cap = %v\n", len(s2), cap(s2))
+  fmt.Printf("s3: len = %v cap = %v\n", len(s3), cap(s3))
+
+}

chapter_04/exercise_4.12/main.go

@@ -0,0 +1,82 @@
+package main
+
+import "fmt"
+
+func linked() (int, int, int) {
+
+  s1 := []int{1, 2, 3, 4, 5}
+  s2 := s1
+  s3 := s1[:]
+  s1[3] = 99
+  return s1[3], s2[3], s3[3]
+
+}
+
+func noLink() (int, int) {
+
+  s1 := []int{1, 2, 3, 4, 5}
+  s2 := s1
+  s1 = append(s1, 6)
+  s1[3] = 99
+  return s1[3], s2[3]
+
+}
+
+func capLinked() (int, int) {
+
+  s1 := make([]int, 5, 10)
+  s1[0], s1[1], s1[2], s1[3], s1[4] = 1, 2, 3, 4, 5
+  s2 := s1
+  s1 = append(s1, 6)
+  s1[3] = 99
+  return s1[3], s2[3]
+
+}
+
+func capNoLink() (int, int) {
+
+  s1 := make([]int, 5, 10)
+  s1[0], s1[1], s1[2], s1[3], s1[4] = 1, 2, 3, 4, 5
+  s2 := s1
+  s1 = append(s1, []int{10: 11}...)
+  s1[3] = 99
+  return s1[3], s2[3]
+
+}
+
+func copyNoLink() (int, int, int) {
+
+  s1 := []int{1, 2, 3, 4, 5}
+  s2 := make([]int, len(s1))
+  copied := copy(s2, s1)
+  s1[3] = 99
+  return s1[3], s2[3], copied
+
+}
+
+func appendNoLink() (int, int) {
+
+  s1 := []int{1, 2, 3, 4, 5}
+  s2 := append([]int{}, s1...)
+  s1[3] = 99
+  return s1[3], s2[3]
+
+}
+
+func main() {
+
+  l1, l2, l3 := linked()
+  fmt.Println("Linked:         ", l1, l2, l3)
+  nl1, nl2 := noLink()
+  fmt.Println("No Link:        ", nl1, nl2)
+  cl1, cl2 := capLinked()
+  fmt.Println("Cap Linked:     ", cl1, cl2)
+  cn1, cn2 := capNoLink()
+  fmt.Println("Cap no Link:    ", cn1, cn2)
+  copy1, copy2, copied := copyNoLink()
+  fmt.Print("Copy No Link:    ", copy1, copy2)
+  fmt.Printf(" (Number of elements copied: %v\n", copied)
+  a1, a2 := appendNoLink()
+  fmt.Println("Append No Link: ", a1, a2)
+
+}