parser.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

const (
	TOKEN_LPAREN = iota
	TOKEN_RPAREN
	TOKEN_NUMBER
	TOKEN_SYMBOL
)

type Token struct {
	kind  int
	value string
}

func tokenize(input string) []string {
	input = strings.Replace(input, "(", " ( ", -1)
	input = strings.Replace(input, ")", " ) ", -1)

	tokens := strings.Fields(input)
	return tokens
}

func build_tokens(tokens []string) []Token {
	var result []Token

	for _, token := range tokens {
		if token == "(" {
			result = append(result, Token{TOKEN_LPAREN, token})
		} else if token == ")" {
			result = append(result, Token{TOKEN_RPAREN, token})
		} else if _, err := strconv.Atoi(token); err == nil {
			result = append(result, Token{TOKEN_NUMBER, token})
		} else {
			result = append(result, Token{TOKEN_SYMBOL, token})
		}
	}
	return result
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)

	for {
		scanner.Scan()
		text := scanner.Text()
		fmt.Println(">", text)

		tokens := tokenize(text)
		token_structure := build_tokens(tokens)
		for _, token := range token_structure {
			fmt.Println(token)
		}
	}
}