Go 基础学习

package main
import (
    "fmt"
    "math"
    "math/cmplx"
)
var (
    aa = 3
    ss = "kkk"
    bb = true
)
func variableZeroValue() {
    var a int
    var s string
    fmt.Printf("%d %q\n", a, s)
}
func variableInitialValue() {
    var a, b int = 3, 4
    var s string = "abc"
    fmt.Println(a, b, s)
}
func variableTypeDeduction() {
    var a, b, c, s = 3, 4, true, "def"
    fmt.Println(a, b, c, s)
}
func variableShorter() {
    a, b, c, s := 3, 4, true, "def"
    b = 5
    fmt.Println(a, b, c, s)
}
func euler() {
    //复数
    c := 3 + 4i
    fmt.Println(cmplx.Abs(c))
    fmt.Printf("%.3f\n",
        cmplx.Exp(1i*math.Pi)+1)
}
func triangle() {
    var a, b int = 3, 4
    fmt.Println(calcTriangle(a, b))
}
func calcTriangle(a, b int) int {
    var c int
    c = int(math.Sqrt(float64(a*a + b*b)))
    return c
}
func consts() {
    const (
        filename = "abc.txt"
        a, b     = 3, 4
    )
    var c int
    c = int(math.Sqrt(a*a + b*b))
    fmt.Println(filename, c)
}
func enums() {
    const (
        cpp        = iota
        _
        python
        golang
        javascript
    )
    const (
        b  = 1 << (10 * iota)
        kb
        mb
        gb
        tb
        pb
    )
    fmt.Println(cpp, javascript, python, golang)
    fmt.Println(b, kb, mb, gb, tb, pb)
}
func main() {
    fmt.Println("Hello world")
    //变量
    variableZeroValue()
    variableInitialValue()
    variableTypeDeduction()
    variableShorter()
    fmt.Println(aa, ss, bb)
    //欧拉公式
    euler()
    //强制类型转换
    triangle()
    //常量
    consts()
    //枚举
    enums()
}