Re: Welcome

From: [at]} <Gérard>
Date: Fri, 26 Oct 2007 15:19:01 +0200

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info{([at]})nowhere.xy
>> -----Original Message-----
>> From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
>> Campbell, Robert D (SELEX) (UK Edinburgh)
>> Sent: Friday, 26 October 2007 6:14 PM
>> To: BLACKBOX{([at]})nowhere.xy
>> Subject: Re: Welcome
>>
>> Hi
>>
>> Am I missing something, or is this an error?
>>
>> The code below does not compile, but if I remove
>> the word 'LIMITED' it does. I thought that LIMITED records were not
>> limited in their defining module.
>>
>>
>> Cheers
>>
>> Robert
>>
>>
>>
>> MODULE DemoTest;
>>
>> TYPE
>> Ball* = POINTER TO LIMITED RECORD
>> radius : REAL
>> END;
>>
>> PROCEDURE Copy* (a : Ball) : Ball;
>> VAR
>> b : Ball;
>> BEGIN
>> NEW (b); b^ := a^; RETURN b
>> END Copy;
>>
>> END DemoTest.
>>
>>
>
> Looks like an error to me.
>
> b.radius := a.radius
>
> which does compile, has the same end result in this example.
>
> Regards,
> Chris Burrows
>
> CFB Software
> http://www.cfbsoftware.com/gpcp
>
>
> ----
> To unsubscribe, send a message with body "SIGNOFF BLACKBOX" to LISTSERV{([at]})nowhere.xy
>
This problem is not limited to... LIMITED records. It's just that a^ and
b^ are not assignment compatible. As 'a' may be an extension of 'b' (at
least in theory, but I suppose the compiler doesn't verify this point),
'a^' may be bigger than 'b^', so that the assignment is impossible.
If you remove the word 'LIMITED', there may be no extension of 'Ball',
and the problem vanishes.

Cheers,

Gérard

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Received on Fri Oct 26 2007 - 15:19:01 UTC