simple DOL-System

dol_system.go

package main

import (
  "bytes"
  "fmt"
)

type ProductionSet map[rune]string
type Alphabet map[rune]bool

type DOLSystem struct {
	Alphabet
	Axiom       string
	Productions ProductionSet
}

func (s *DOLSystem) Next() string {
	var buf bytes.Buffer
	for _, r := range s.Axiom {
		p, ok := s.Productions[r]
		if !ok {
			panic("no production exists for rune " + string(r))
		}
		buf.WriteString(p)
	}
	n := buf.String()
	s.Axiom = n
	return n
}

func NewDOLSystem(V Alphabet, axiom string, P ProductionSet) *DOLSystem {
	return &DOLSystem{V, axiom, P}
}

func main() {
	s := DOLSystem{
		Alphabet{'a': true, 'b': true},
		"a",
		ProductionSet{'a': "ab", 'b': "a"},
	}
	for i := 0; i < 5; i++ {
		fmt.Println(s.Next())
	}
}