函数类型

package main

import "fmt"

func sum(a, b int) int {
    return a + b
}

func sumArgs(args ...int) int {

    var sum int
    for _, v := range args {
        sum += v
    }
    return sum
}

func Sum(args ...int) int {
    // 利用 ... 来解序列
    result := sumArgs(args...)
    return result
}
func MyPrintf(args ...interface{}) {
    for _, arg := range args {
        fmt.Println(arg)
        switch arg.(type) {
        case int:
            fmt.Println("int", arg)
        case string:
            fmt.Println("string", arg)
        case float32:
            fmt.Println("float")
        default:
            fmt.Println("err", arg)
        }

    }
}

// 定义函数类型
type Greeting func(name string) string

func (g Greeting) say(n string) {
    fmt.Println(g(n))
}

func english(n string) string {
    return "english " + n
}

func main() {
    fmt.Println(sum(1, 2))
    fmt.Println(sumArgs(1, 2, 3, 4))
    var v1 int = 1
    var v2 int64 = 234
    var v3 string = "hello"
    var v4 float32 = 1.234
    MyPrintf(v1, v2, v3, v4)
    fmt.Println(Sum(1, 2, 3, 4, 5))

    //转换成 Greeting 类型的函数对象
    g := Greeting(english)
    // var g2 Greeting = english
    var g2 Greeting = english
    g2.say("g2")
    g.say("hi")
}