Go iota关键字与枚举类型实现原理

const (
    a int = iota // 0
    b            // 1
    c            // 2
    d            // 3
)

const ( 
    a = iota // 0 
    b        // 1 
    c        // 2 
    _ 
    _ 
    d        // 5 
)

type Allergen int
const (
    IgEggs Allergen = 1 << iota // 1 << 0 which is 00000001 = 1
    IGChocolate                 // 1 << 1 which is 00000010 = 2
    IgNuts                      // 1 << 2 which is 00000100 = 4
    IgStrawberries              // 1 << 3 which is 00001000 = 8
    Igshellfish                 // 1 << 4 which is 00010000 = 16
)

const (
    a, q int = iota, iota + 1 // 0, 1
    b, w                      // 1, 2
    c, e                      // 2, 3
    d, r                      // 3, 4
)

type Season int

const (
	Summer Season = 1
	Autumn        = 2
	Winter        = 3
	spring        = 4
)

type Season int

const (
	Summer Season = iota + 1
	Autumn        
	Winter        
	Spring        
)