class Env {
  const _outer Env
  var _data StringMap<MalVal> = {}

  def new(outer Env) {
    _outer = outer
  }

  def new(outer Env, binds List<MalVal>, exprs List<MalVal>) {
    _outer = outer
    for i in 0..binds.count {
      const name = (binds[i] as MalSymbol).val
      if name == "&" {
        const restName = (binds[i + 1] as MalSymbol).val
        _data[restName] = MalList.new(exprs.slice(i))
        break
      } else {
        _data[name] = exprs[i]
      }
    }
  }

  def find(key MalSymbol) Env {
    if key.val in _data { return self }
    return _outer?.find(key)
  }

  def get(key MalSymbol) MalVal {
    const env = find(key)
    if env == null { throw MalError.new("'" + key.val + "' not found") }
    return env._data[key.val]
  }

  def set(key MalSymbol, value MalVal) MalVal {
    _data[key.val] = value
    return value
  }
}