基本儲存型態、變數以及迴圈用法
數值計算
-
各型態
- string, integer, floats, booleans, booleans operaters
package main
import "fmt"
func main() {
fmt.Println("go" + "lang")
fmt.Println("1+1 =", 1+1)
fmt.Println("7.0/3.0 =", 7.0/3.0)
fmt.Println(true && false)
fmt.Println(true || false)
fmt.Println(!true)
}
- string可以直接做相加合併,其他如同C/C++規則
- 變數宣告使用
package main
import "fmt"
func main() {
var a = "initial"
fmt.Println(a)
var b, c int = 1, 2
fmt.Println(b, c)
var d = true
fmt.Println(d)
var e int
fmt.Println(e)
f := "apple"
fmt.Println(f)
}
-
可以一次宣告多個變數。且比較特殊的是最後的:=。他是一個簡化的宣告,可以依據後方的內容去決定var的型態。
- const用法
package main
import (
"fmt"
"math"
)
const s string = "constant"
func main() {
fmt.Println(s)
const n = 500000000
const d = 3e20 / n
fmt.Println(d)
fmt.Println(int64(d))
fmt.Println(math.Sin(n))
}
- 可以宣告在各 var的位置前。但是在指定變數型態之前都是不確定型態的,如最後的d
fmt.Println(d)
//6e+11
fmt.Println(int64(d))
//600000000000
- For迴圈
package main
import "fmt"
func main() {
i := 1
for i <= 3 {
fmt.Println(i)
i = i + 1
}
for j := 0; j < 3; j++ {
fmt.Println(j)
}
for i := range 3 {
fmt.Println("range", i)
}
for {
fmt.Println("loop")
break
}
for n := range 6 {
if n%2 == 0 {
continue
}
fmt.Println(n)
}
}
-
這邊介紹了幾種for迴圈的方式,與C/c++不同不需要"()",且也支援range。還有一個用法是倒數遞二種,for 然後沒有接任何condition的用法。他會執行到讀取到break為止。在示範中print一次"loop"字串就結束了。
- IF/else 用法跟 c 一樣
package main
import "fmt"
func main() {
if 7%2 == 0 {
fmt.Println("7 is even")
} else {
fmt.Println("7 is odd")
}
if 8%4 == 0 {
fmt.Println("8 is divisible by 4")
}
if 8%2 == 0 || 7%2 == 0 {
fmt.Println("either 8 or 7 are even")
}
if num := 9; num < 0 {
fmt.Println(num, "is negative")
} else if num < 10 {
fmt.Println(num, "has 1 digit")
} else {
fmt.Println(num, "has multiple digits")
}
}
- swith 用法也與C 相同
package main
import (
"fmt"
"time"
)
func main() {
i := 2
fmt.Print("Write ", i, " as ")
switch i {
case 1:
fmt.Println("one")
case 2:
fmt.Println("two")
case 3:
fmt.Println("three")
}
switch time.Now().Weekday() {
case time.Saturday, time.Sunday:
fmt.Println("It's the weekend")
default:
fmt.Println("It's a weekday")
}
t := time.Now()
switch {
case t.Hour() < 12:
fmt.Println("It's before noon")
default:
fmt.Println("It's after noon")
}
whatAmI := func(i interface{}) {
switch t := i.(type) {
case bool:
fmt.Println("I'm a bool")
case int:
fmt.Println("I'm an int")
default:
fmt.Printf("Don't know type %T\n", t)
}
}
whatAmI(true)
whatAmI(1)
whatAmI("hey")
}
參考網站: gobyexample
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