Go言語のデータ型と配列、スライス、マップ

基本のデータ型

string, int, float64, bool, nil
初期値

var s string //""
var a int //0
var f bool //false

変数

func main(){
  var msg string
  msg = "hello world"
  var msg1 string = "hello world1"
  var msg2 = "hello world2" //stringは省略可能
  msg3 := "hello world3" //値と変数の紐付け
  fmt.Println(msg)
  fmt.Println(msg1)
  fmt.Println(msg2)
  fmt.Println(msg3)
  
  a, b := 1, 2 //複数宣言
  fmt.Println(a)
  fmt.Println(b)
  
  var (
    c = 1
    d = "test"
  )
}

配列

func main(){
  var a [5]int
  b := [3]int{1, 3, 5} //型の宣言と同時に値を代入
  c := [...]int{1, 3, 5, 6} //値はわかっているので指定する必要なし
  fmt.Println(a)
  fmt.Println(b)
  fmt.Println(c)
}

配列の展開

func main() {
	array1 := []int{1, 2, 3}
	array2 := []int{4, 5, 6}
	array3 := append(array1, array2...)

	fmt.Println(array1)
	fmt.Println(array2)
	fmt.Println(array3)
}

[1 2 3]
[4 5 6]
[1 2 3 4 5 6]

スライス1

func main(){
  a := [5]int{9, 8, 7, 6, 5}
  s := a[0:3]
  s[0] = 12
  fmt.Println(a)//[12 8 7 6 5]
  fmt.Println(s)//[12 8 7]
  fmt.Println(len(s))//3
  fmt.Println(cap(s))//5 0から切り出せる最大の値
}

スライス2

func main(){
  s := make([]int, 3)
  s2 := []int{1, 3, 5}
  fmt.Println(s)//[0 0 0]]
  fmt.Println(s2)//[1 3 5]
  s2 = append(s2, 10)
  fmt.Println(s2)//[1 3 5 10]
  s3 := make([]int, len(s2))
  num := copy(s3, s2)
  fmt.Println(s3)//[1 3 5 10]
  fmt.Println(num)//4
}

スライス3

func main(){
  cards := []string{newCard(), "Ace of Dia"}
  cards = append(cards, "Six of Spades")

  for i, card := range cards {
    fmt.Println(i, card)
  }
}

マップ

func main() {
  m := make(map[string]int)
  m["japan"] = 100
  m["ame"] = 200
  fmt.Println(m)
  delete(m, "japan")
  fmt.Println(m)
  m2 := map[string]int{"tokyo":1, "osaka":2}
  fmt.Println(m2)

  m3 := make(map[string]string)
  m3["japan"] = "no1"
  m3["ame"] = "no2"
  fmt.Println(m3)
  v1, ok := m3["japan"]
  fmt.Println(v1)//no1
  fmt.Println(ok)//true

  v2, ng := m3["canada"]
  fmt.Println(v2)
  fmt.Println(ng)//false
}