整数を表す文字列を受理するオートマトン②

以前作った整数のオートマトン、文字列"01"を受理するかどうかはさておき、"0"を受理しないのは問題だと思うので修正した。

class IntChecker : Checker
{
  enum IntParsingState
  {
    Error,
    State0,
    State1,
    State2,
    State3,
  }

  IntParsingState _state;

  public IntChecker()
  {
    Reset();
  }

  public void Reset()
  {
    _state = IntParsingState.State0;
  }

  public void Next(char ch)
  {
    switch (_state)
    {
      case IntParsingState.State0:
        if (ch == '-' ||
          ch == '+')
        {
          _state = IntParsingState.State1;
        }
        else if (ch == '1' ||
          ch == '2' ||
          ch == '3' ||
          ch == '4' ||
          ch == '5' ||
          ch == '6' ||
          ch == '7' ||
          ch == '8' ||
          ch == '9')
        {
          _state = IntParsingState.State2;
        }
        else if (ch == '0')
        {
          _state = IntParsingState.State3;
        }
        else
        {
          _state = IntParsingState.Error;
        }
        break;
      case IntParsingState.State1:
        if (ch == '1' ||
          ch == '2' ||
          ch == '3' ||
          ch == '4' ||
          ch == '5' ||
          ch == '6' ||
          ch == '7' ||
          ch == '8' ||
          ch == '9')
        {
          _state = IntParsingState.State2;
        }
        else if (ch == '0')
        {
          _state = IntParsingState.State3;
        }
        else
        {
          _state = IntParsingState.Error;
        }
        break;
      case IntParsingState.State2:
        if (ch == '0' ||
          ch == '1' ||
          ch == '2' ||
          ch == '3' ||
          ch == '4' ||
          ch == '5' ||
          ch == '6' ||
          ch == '7' ||
          ch == '8' ||
          ch == '9')
        {
          _state = IntParsingState.State2;
        }
        else
        {
          _state = IntParsingState.Error;
        }
        break;
      case IntParsingState.State3:
      case IntParsingState.Error:
        _state = IntParsingState.Error;
        break;
    }
  }

  public bool IsAcceptable()
  {
    return
      _state == IntParsingState.State2 ||
      _state == IntParsingState.State3;
  }

  public bool IsError()
  {
    return _state == IntParsingState.Error;
  }
}

動かしてみた

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