Golang对逆波兰表示法的简单实现

package main
import (
    "bufio"
    "fmt"
    "os"
    "strconv"
)
type Stack struct {
    i int
    data [10]int
}
func (s *Stack) Push(a int) {
    fmt.Printf("push:data:%d,pos:%d\n", a, s.i)
    s.data[s.i] = a
    s.i++
}
func (s *Stack) Pop() int {
    s.i--
    return s.data[s.i]
}

var reader *bufio.Reader = bufio.NewReader(os.Stdin)
var st Stack
func main() {
    for {
        s, err := reader.ReadString('\n')
        var token string
        if err != nil {
            println("Good Bye!")
            continue
        }
        for _, c := range s {
            switch {
            case c >= '0' && c <= '9':
                token += string(c)
            case c == ' ':    // 一个数输入结束
                if token != "" {
                    r, _ := strconv.Atoi(token)
                    st.Push(r)
                    token = ""
                }
            case c == '+':
                st.Push(st.Pop() + st.Pop())
            case c == '*':
                st.Push(st.Pop() * st.Pop())
            case c == '-':
                p := st.Pop()
                q := st.Pop()
                st.Push(q-p)
            case c == '/':
                p := st.Pop()
                q := st.Pop()
                if p != 0 {
                    st.Push(q/p)
                } else {
                    fmt.Printf("divisor couldn't be zero\n")
                }
            case c == '\n':
                fmt.Printf("%d\n",st.Pop());
            case c == 'q':
                return
            
            }
        }
    }
}