Re: [BLACKBOX] RECORDs and ARRAYs

From: [at]} <Chris>
Date: Mon, 16 Mar 2009 15:02:41 +1030

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Doug,

Maybe I'm missing something but why do you want to use a method to process
the array rather than a procedure?

Why not:

  PROCEDURE Norm (IN x: ARRAY): REAL;
    VAR i: INTEGER; d2, norm: REAL;
  BEGIN
    FOR i := 0 TO LEN(r.x)-1 DO d2 := d2 + r.x[i]*r.x[i] END;
    norm := Math.Sqrt(d2);
    RETURN norm
  END Norm;
        
So that for
  
  VAR
    x: Array;
    norm: REAL;

One would call
        
  norm := Norm(x);

--
Chris Burrows
CFB Software
Armaide: ARM Oberon-07 Development System for Windows
http://www.cfbsoftware.com/armaide
________________________________
	From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xyDouglas G. Danforth
	Sent: Monday, 16 March 2009 2:25 PM
	To: BLACKBOX{([at]})nowhere.xy	Subject: [BLACKBOX] RECORDs and ARRAYs
	
	
	This is a grumble.
	If you have a good suggestion then I would like to hear it.
	
	Why do I have to wrap arrays in records just so I can have methods
	that operate on the arrays?  Why can't I have methods for arrays?
	
	Here is what is currently necessary to get a method for an array
	    TYPE
	       Array = POINTER TO ARRAY OF REAL;
	       ArrayRec = POINTER TO RECORD (x: Array) END;
	
	    PROCEDURE (r: ArrayRec) Norm (): REAL;
	       VAR i: INTEGER; d2, norm: REAL;
	    BEGIN
	       FOR i := 0 TO LEN(r.x)-1 DO d2 := d2 + r.x[i]*r.x[i] END;
	       norm := Math.Sqrt(d2);
	       RETURN norm
	    END Norm;
	
	Here is what I would rather like to do
	
	    PROCEDURE (x: Array) Norm (): REAL;
	       VAR i: INTEGER; d2, norm: REAL;
	    BEGIN
	       FOR i := 0 TO LEN(x)-1 DO d2 := d2 + x[i]*x[i] END;
	       norm := Math.Sqrt(d2);
	       RETURN norm
	    END Norm;
	
	So that for
	    VAR
	       r:   ArrayRec;
	       x:   Array;
	       norm:   REAL;
	One would call
	
	    norm := x.Norm();
	rather than
	    norm := r.Norm();
	
	With array methods the code is more efficient (less dereferencing)
and cleaner.
	
	Now what does this break?  Why wasn't this done?  Where is the error
in my thoughts?
	
	-Doug Danforth
	
	
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Received on Mon Mar 16 2009 - 05:32:41 UTC