### For
Go has only one looping construct, the for loop
func main(){
sum := 0;
for i := 0; i < 10; i++ {
sum += i
}
fmt.Println(sum)
}
The init and post statements are optional
func main(){
sum := 1;
for ; sum < 1000; {
sum += sum
}
fmt.Println(sum)
}
For is Go’s “while”
At that point you can drop the semicolons: C’s while is spelled for in Go.
func main(){
sum := 1;
for sum < 1000 {
sum += sum
}
fmt.Println(sum)
}
### If
Go’s if statements are like its for loops.
func sqrt(x float64) string {
if x < 0 {
return sqrt(-x) + "i"
}
return fmt.Sprint(math.Sqrt(x))
}
func main(){
fmt.Println(sqrt(2), sqrt(-4))
}
If with a short statement
func pow(x, n, lim float64) float64 {
if v := math.Pow(x, n); v < lim {
return v
} else {
fmt.Printf("%g >= %g\n", v, lim)
}
return lim
}
func main(){
fmt.Println(
pow(3, 2, 10),
pow(3, 3, 20),
)
}
### Switch
A switch statement is a shorter way to write a sequence of if – else statements.
func main(){
fmt.Print("Go runs on ")
switch os := runtime.GOOS; os{
case "darwin":
fmt.Println("OS X.")
case "linux":
fmt.Println("Linux.")
default:
fmt.Println("%s.\n", os)
}
}
func main(){
fmt.Print("When's Saturday?")
today := time.Now().Weekday()
switch time.Saturday{
case today + 0:
fmt.Println("Today.")
case today + 1:
fmt.Println("Tommorow.")
case today + 2:
fmt.Println("In two days.")
default:
fmt.Println("Too far away.")
}
}
func main(){
t := time.Now()
switch {
case t.Hour() < 12:
fmt.Println("Good morning!")
case t.Hour() < 17:
fmt.Println("Good afternoon.")
default:
fmt.Println("Good evening.")
}
}
### Defer
A defer statement defers the execution of a function until the surrounding function returns.
func main(){
defer fmt.Println("wrold")
fmt.Println("hello")
}
$ go build hello.go && ./hello
hello
wrold
Stacking defers
L Deferred function calls are pushed onto a stack.
func main(){
fmt.Println("counting")
for i := 0; i < 10; i++ {
defer fmt.Println(i)
}
fmt.Println("done")
}
deferってのは使い方がよくわからんが、最初は参照しながら書けば問題なさそうです。
