golang创建优雅的类型定义

package main

import "fmt"

const (
    A = 1 << iota // 1 << 0 which is 00000001
    B             // 1 << 1 which is 00000010
    C             // 1 << 2 which is 00000100
    D             // 1 << 3 which is 00001000
    E             // 1 << 4 which is 00010000
)

func main() {

    /*
        print:
            has A
            has C
            has E
    */
    check(A | C | E)

}

func check(flag int) {

    if flag&A == A {
        fmt.Println("has A")
    }

    if flag&B == B {
        fmt.Println("has B")
    }

    if flag&C == C {
        fmt.Println("has C")
    }

    if flag&D == D {
        fmt.Println("has D")
    }

    if flag&E == E {
        fmt.Println("has E")
    }

}