GO语言基础语法 | 青训营笔记

1.变量

    package main
    import (
            "fmt"
            "math"
    )
    func main() {
            fmt.Println("hello world")
            var a = "hello"
            var b, c int = 1, 2
            var d = true
            var e float64
            f := float32(e)
            g := a + "foo"
            fmt.Println(a, b, c, d, e, f)
            fmt.Println(g)

            const s string = "constant"
            const h = 500000000
            const i = 3e20
            fmt.Println(s, h, i, math.Sin(h), math.Sin(i))
    }

2.if...else...

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")
	}

	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")
	}
}

3.for

package main

import (
	"fmt"
)

func main() {
	i := 1
	for j := 7; j < 9; j++ {
		fmt.Println(j)
	}

	for n := 0; n < 5; n++ {
		if n%2 == 0 {
			continue
			// break
		}
		fmt.Println(n)
	}
	for i <= 3 {
		fmt.Println(i)
		i = i + 1
	}
}

4.switch

package main

import (
	"fmt"
)

func main() {
	a := 2
	switch a {
	case 1:
		fmt.Println("one")
	case 2:
		fmt.Println("two")
	case 3:
		fmt.Println("three")
	case 4, 5:
		fmt.Println("four or five")
	default:
		fmt.Println("default")
	}
}

5.数组

package main

import (
	"fmt"
)

func main() {
	var a [5]int
	a[4] = 100
	fmt.Println(a[4], len(a))

	b := [5]int{1, 2, 3, 4, 5}
	fmt.Println(b)

	var twoD [2][3]int
	for i := 0; i < 2; i++ {
		for j := 0; j < 3; j++ {
			twoD[i][j] = i + j
		}
	}
	fmt.Println("2d:", twoD)
}

6.切片

package main

import (
	"fmt"
)

func main() {
	s := make([]string, 3)
	s[0] = "a"
	s[1] = "b"
	s[2] = "c"
	fmt.Println("get:", s[2])
	fmt.Println("len:", len(s))

	s = append(s, "d")
	s = append(s, "e", "f")

	c := make([]string, len(s))
	copy(c, s)
	fmt.Println(c)

	fmt.Println(s[2:5])
	fmt.Println(s[:5])
	fmt.Println(s[2:])

	good := []string{"g", "o", "o", "d"}
	fmt.Println(good)

}