fsm.go

package main

import (
	"fmt"
)

type Action struct {
	Next interface{}
	f    func()
}

type Transition map[interface{}]Action
type Transitions map[interface{}]Transition

type FSM struct {
	Start       interface{}
	Transitions Transitions
	Final       map[interface{}]bool
}

func (fsm *FSM) Parse(input string) {

	cur := fsm.Start
	size := len(input)
	ts := fsm.Transitions

	for i := 0; i < size; i++ {
		c := rune(input[i])

		t := interface{}(ts[cur]).(Transition)

		action, ok := interface{}(t[c]).(Action)

		if !ok {
			cur = nil
			break
		}

		cur = action.Next
		f := action.f

		if f != nil {
			f()
		}

	}

	fmt.Println("valid:", fsm.Final[cur], cur)
}

func main() {

	fsm := FSM{
		Start:       1,
		Transitions: make(Transitions),
		Final: map[interface{}]bool{
			3: true,
		},
	}

	ts := fsm.Transitions

	ts[1] = Transition{
		'a': Action{
			2,
			func() {},
		},
	}

	ts[2] = Transition{
		'i': Action{
			3,
			func() {},
		},
	}

	ts[3] = Transition{}

	fsm.Parse("ai")

}