I'm porting some code from Java to D and am getting stuck on what Java calls static class fields.  I can't find out how to write the functional (or best practices) equivalent in D.

(There are other syntax errors in D code, I'm fixing them one by one)

######### Begin D code (ported from Java code below, and I probably should use
an Enum, but .... haven't)
public class Answer
{
/* I've tried various combinations of syntax here */
  static int CORRECT = 0;
  public const int WRONG = 1;

  private int _answerCode;
  private string _answerText;

  /*
  */
  public this(int answerCode, string answerText)
  {
    _answerCode = answerCode;
    _answerText = answerText;
  }

  /*
  */
  public int getAnswerCode()
  {
    return _answerCode;
  }

  /*
  */
  public string getAnswerText()
  {
    return _answerText;
  }
}
####### End D code code

####### Begin Java code (included to show how it was done in java)
public class Answer
{
  public static final int CORRECT = 0;
  public static final int WRONG = 1;

  private int _answerCode;
  private String _answerText;

  /*
  */
  public Answer(int answerCode, String answerText)
  {
    _answerCode = answerCode;
    _answerText = answerText;
  }

  /*
  */
  public int getAnswerCode()
  {
    return _answerCode;
  }

  /*
  */
  public String getAnswerText()
  {
    return _answerText;
  }
}
###### End Java code

######### Begin D code snippet trying to use the Answer class int asd = Answer.CORRECT; <-- compile error here

try
{
  answer = problem.getAnswer(reply); // grade answer

  if (answer.getAnswerCode() == Answer.CORRECT) <-- compile error here
    inOut.displayAnswer("Correct");
  else
    inOut.displayAnswer("Nope, " ~ answer.getAnswerText());
}
catch (Exception iae)
{
  inOut.displayAnswer(iae.getMessage());
  repeatQuestion = true; // show same question again
}
######### End D code snippet

%u <throwaway@limewall.org> wrote:

> I'm porting some code from Java to D and am getting stuck on what Java calls
> static class fields.  I can't find out how to write the functional (or best
> practices) equivalent in D.
[snip]
>   static int CORRECT = 0;
[snip]
> int asd = Answer.CORRECT; <-- compile error here
[snip]
>   if (answer.getAnswerCode() == Answer.CORRECT) <-- compile error here

The default access level in D is private, so CORRECT will not be
available outside the module in which Answer is defined.

As you mention, you should probably use an enum for wrong/correct.
However, due to lookup rules, an embedded enum would require users to
specify Answer.Correctness.CORRECT/WRONG, so separate enums for each
might be a better idea.

The most common way to expose the stored values in D code would probably
be as properties:

class Answer {
    alias int Correctness;
    enum Correctness CORRECT = 0;
    enum Correctness WRONG = 1;

    Correctness _answerCode;
    string _answerText;

    @property Correctness answerCode( ) const {
        return _answerCode;
    }

    @property string answerText( ) const {
        return _answerText;
    }
}

-- 
Simen

Simen kjaeraas:
> class Answer {
>      alias int Correctness;
>      enum Correctness CORRECT = 0;
>      enum Correctness WRONG = 1;
> 
>      Correctness _answerCode;
>      string _answerText;
> 
>      @property Correctness answerCode( ) const {
>          return _answerCode;
>      }

'Correctness' there begs to be a typedef :-]

Bye,
bearophile

bearophile <bearophileHUGS@lycos.com> wrote:

> Simen kjaeraas:
>> class Answer {
>>      alias int Correctness;
>>      enum Correctness CORRECT = 0;
>>      enum Correctness WRONG = 1;
>>
>>      Correctness _answerCode;
>>      string _answerText;
>>
>>      @property Correctness answerCode( ) const {
>>          return _answerCode;
>>      }
>
> 'Correctness' there begs to be a typedef :-]

Don't I know it. But typedefs are supposed to go away.

-- 
Simen

bearophile wrote:

> Simen kjaeraas:
>> class Answer {
>>      alias int Correctness;
>>      enum Correctness CORRECT = 0;
>>      enum Correctness WRONG = 1;
>> 
>>      Correctness _answerCode;
>>      string _answerText;
>> 
>>      @property Correctness answerCode( ) const {
>>          return _answerCode;
>>      }
> 
> 'Correctness' there begs to be a typedef :-]
> 
> Bye,
> bearophile

I think it wants to go boolean.

On 2010-08-08 21:12, %u wrote:
> I'm porting some code from Java to D and am getting stuck on what Java calls
> static class fields.  I can't find out how to write the functional (or best
> practices) equivalent in D.
>
> (There are other syntax errors in D code, I'm fixing them one by one)
>
> ######### Begin D code (ported from Java code below, and I probably should use
> an Enum, but .... haven't)
> public class Answer
> {
> /* I've tried various combinations of syntax here */
>    static int CORRECT = 0;
>    public const int WRONG = 1;
>
>    private int _answerCode;
>    private string _answerText;
>
>    /*
>    */
>    public this(int answerCode, string answerText)
>    {
>      _answerCode = answerCode;
>      _answerText = answerText;
>    }
>
>    /*
>    */
>    public int getAnswerCode()
>    {
>      return _answerCode;
>    }
>
>    /*
>    */
>    public string getAnswerText()
>    {
>      return _answerText;
>    }
> }
> ####### End D code code
>
> ####### Begin Java code (included to show how it was done in java)
> public class Answer
> {
>    public static final int CORRECT = 0;
>    public static final int WRONG = 1;
>
>    private int _answerCode;
>    private String _answerText;
>
>    /*
>    */
>    public Answer(int answerCode, String answerText)
>    {
>      _answerCode = answerCode;
>      _answerText = answerText;
>    }
>
>    /*
>    */
>    public int getAnswerCode()
>    {
>      return _answerCode;
>    }
>
>    /*
>    */
>    public String getAnswerText()
>    {
>      return _answerText;
>    }
> }
> ###### End Java code
>
> ######### Begin D code snippet trying to use the Answer class
> int asd = Answer.CORRECT;<-- compile error here
>
> try
> {
>    answer = problem.getAnswer(reply); // grade answer
>
>    if (answer.getAnswerCode() == Answer.CORRECT)<-- compile error here
>      inOut.displayAnswer("Correct");
>    else
>      inOut.displayAnswer("Nope, " ~ answer.getAnswerText());
> }
> catch (Exception iae)
> {
>    inOut.displayAnswer(iae.getMessage());
>    repeatQuestion = true; // show same question again
> }
> ######### End D code snippet

I don't know how you are trying to use your class but I don't see any errors in your code.

-- 
/Jacob Carlborg

On 2010-08-08 21:28, Simen kjaeraas wrote:
> %u <throwaway@limewall.org> wrote:
>
>> I'm porting some code from Java to D and am getting stuck on what Java
>> calls
>> static class fields. I can't find out how to write the functional (or
>> best
>> practices) equivalent in D.
> [snip]
>> static int CORRECT = 0;
> [snip]
>> int asd = Answer.CORRECT; <-- compile error here
> [snip]
>> if (answer.getAnswerCode() == Answer.CORRECT) <-- compile error here
>
> The default access level in D is private, so CORRECT will not be
> available outside the module in which Answer is defined.

Since when is the default access level in D private?

> As you mention, you should probably use an enum for wrong/correct.
> However, due to lookup rules, an embedded enum would require users to
> specify Answer.Correctness.CORRECT/WRONG, so separate enums for each
> might be a better idea.
>
> The most common way to expose the stored values in D code would probably
> be as properties:
>
> class Answer {
> alias int Correctness;
> enum Correctness CORRECT = 0;
> enum Correctness WRONG = 1;
>
> Correctness _answerCode;
> string _answerText;
>
> @property Correctness answerCode( ) const {
> return _answerCode;
> }
>
> @property string answerText( ) const {
> return _answerText;
> }
> }
>


-- 
/Jacob Carlborg

Jacob Carlborg <doob@me.com> wrote:

> Since when is the default access level in D private?

Uhm, since I made it up? Sorry about that, I believe I
mixed it up with C++.

-- 
Simen