Newsgroups: comp.lang.pascal
Path: utzoo!utgpu!watserv1!watmath!nmouawad
From: nmouawad@watmath.waterloo.edu (Naji Mouawad)
Subject: Re: need a little flexibility
Message-ID: <1991Apr24.235739.25115@watmath.waterloo.edu>
Organization: University of Waterloo
References: <1991Apr24.183315.7997@ux1.cso.uiuc.edu>
Date: Wed, 24 Apr 1991 23:57:39 GMT
Lines: 57

In article <1991Apr24.183315.7997@ux1.cso.uiuc.edu> amead@s.psych.uiuc.edu (alan mead) writes:
>Hi.  I want to manipulate a data structure in the cleanest way possible 
>(after I write this, I'd like to minimize maintenance time).  I've been
>working with something like this:
>
>Block = record
>       x    : byte;
>       y    : byte;
>       ...
>       data : array[1..252] of byte;
>end;
>
>but the elements of data are sometimes words instead of bytes and this
>structure doesn't compile (I guess you cannot declare ABSOLUTE structures
>in a type declaration?):
>
>Block = record
>       x    : byte;
>       y    : byte;
>       ...
>       data : array[1..252] of byte;
>       dataW: array[1..126] of word ABSOLUTE data;
>end;
>
>And a variant record requires an exhaustive listing of it's fields right?

I don't understand your last statement, it seems that a record of
the following form:

Block = record
   x : byte;
   y : byte;
   case boolean of
    True : (data : array[1..252] of byte);
    False: (dataw: array[1..126] of word);
end;

would do the trick. You could access just as easily data or dataw
as follows:

Var B : block;
    w : word;

Begin
  w := 12345;
  b.data[i] := hi(w);
  b.dataw[i] := w;
end.

Isn't this what you were looking for ?

--Naji.
-- 
     -------------------------------------------------------------------
    | Naji Mouawad  |          nmouawad@watmath.waterloo.edu            |
    |  University   |---------------------------------------------------|
    | Of Waterloo   |   "The Stranger in us is our most familiar Self"  |