Functions and Methods

func div(a, b int) (int, error) {
    if b == 0 { return 0, errors.New("div0") }
    return a / b, nil
}
q, err := div(10, 2)
q  // 5
// err == nil

func split(s string) (head, tail string) {
    head, tail = s[:1], s[1:]
    return
}
h, t := split("ab")
h  // "a"
// t == "b"

type Counter struct{ N int }
func (c *Counter) Inc() { c.N++ }
c := Counter{}
c.Inc()
c.N  // 1

func sum(xs ...int) int {
    n := 0
    for _, x := range xs { n += x }
    return n
}
sum(1, 2, 3)  // 6

// defer fmt.Println(1)
// defer fmt.Println(2)
// prints 2 then 1

add := func(a, b int) int { return a + b }
add(2, 3)  // 5

n := 0
inc := func() { n++ }
inc(); inc()
n  // 2

// func init() { /* setup */ }
// no args, no returns; may have multiple per file

func set(s []int) { s[0] = 9 }
x := []int{1}
set(x)
x[0]  // 9

func makeAdder(k int) func(int) int {
    return func(n int) int { return n + k }
}
makeAdder(10)(5)  // 15

// import _ "net/http/pprof"
// registers handlers via init

type T int
func (t T) V() int { return int(t) }
T.V(T(3))  // 3

c := Counter{N: 1}
f := c.Inc
f()
c.N  // 2

xs := []int{1, 2}
sum(xs...)  // 3

func safe() (ok bool) {
    defer func() {
        if r := recover(); r != nil { ok = false }
    }()
    panic("x")
}
// safe() recovers