Golang 闭包

package main

import (
    "fmt"
)

func adder() func(int) int {
    sum := 0
    return func(x int) int {
        sum += x
        return sum
    }
}

func main() {
    pos, reg := adder(), adder()
    for i := 0; i < 10; i++ {
        fmt.Println(
            i,         //sum[i] = i
            pos(i),    //pos(i) = pos(i).sum + i
            reg(-2*i), //reg(-2 * i) = reg(i) + (-2*i)
        )
    }
}

输出：

API server listening at: 127.0.0.1:26756
0 0 0
1 1 -2
3 2 -6
6 3 -12
10 4 -20
15 5 -30
21 6 -42
28 7 -56
36 8 -72
45 9 -90