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From: wyoung@cis.ksu.edu (William J. Young)
Newsgroups: comp.lang.pascal
Subject: Re: need a little flexibility
Message-ID: <1991Apr26.145543.4741@maverick.ksu.ksu.edu>
Date: 26 Apr 91 14:55:43 GMT
References: <1991Apr24.183315.7997@ux1.cso.uiuc.edu> <1991Apr24.235739.25115@watmath.waterloo.edu> <91115.111155IO92203@MAINE.BITNET>
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In article <91115.111155IO92203@MAINE.BITNET> IO92203@MAINE.BITNET (Scott Maxell) writes:
>In article <1991Apr24.235739.25115@watmath.waterloo.edu>,
>nmouawad@watmath.waterloo.edu (Naji Mouawad) says:
>>
>>Block = record
>>   x : byte;
>>   y : byte;
>>   case boolean of
>>    True : (data : array[1..252] of byte);
>>    False: (dataw: array[1..126] of word);
>>end;
>>
>
>   This last approach won't work as stated because a variant record can
>only contain one of the possible fields declared.

Have you tried it?  It does work.  A variable of a variant record type
does allow accessing either of the named fields.  It's up to the
programmer to do the error checking necessary to avoid misuse.

> The field in the variant
>should also have a declared variable and not just a type.
 ^^^^^^
>
>Type
>  Block = RECORD
>            X,
>            Y : Byte;
>            Case WordData : Boolean OF
>              True  : ( DataW : ARRAY [1..126] OF Word );
>              False : ( Data  : ARRAY [1..252] OF Byte );
>          END;  (* record *)
>
** rest deleted **

Not necessary.  This is nice for doing the error checking I mentioned,
but you can leave it off and access either field as needed.

--
----------------------------
Bill Young 
wyoung@cis.ksu.edu