js s-expr pareser

gistfile1.js

String.prototype.fixSpaces = function () {
  return this.replace(/\s+/g, ' ').trim();
};

var Symbol = String;

function tokenize(s) {
  return s.replace(/([()])/g, ' $1 ').fixSpaces().split(' ');
};

function read(s) {
  return readTokens(tokenize(s));
}

function readTokens(tokens) {
  var token, readed;

  if (tokens.length == 0) {
    throw 'Unexpected end of file';
  }

  token = tokens.shift();

  if (token == '(') {
    readed = [];
    while (tokens[0] != ')') {
      readed.push(readTokens(tokens));
    }
    tokens.shift();
    return readed;
  }
  else if (token == ')') {
    throw 'Unexpected )';
  }

  return atom(token);
}

function atom(token) {
  if (token.match(/^-?(\d+)(\.\d+)?$/)) {
    return Number(token);
  }
  return Symbol(token);
}

function repl() {
  var inp = process.stdin,
      out = process.stdout,
      prompt = '> ';
  inp.setEncoding('utf8');
  out.setEncoding('utf8');

  out.write(prompt);

  inp.resume();
  inp.on('data', function (chunk) {
    console.dir(read(chunk));
    out.write(prompt);
  });
}

repl();