Re: [BLACKBOX] INTEGER Add Has Wrong result

From: Campbell, Robert (SELEX GALILEO, UK) <robert.d.campbell{([at]})nowhere.xy>
Date: Thu, 7 Apr 2011 08:45:01 +0100

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Content-type: text/plain

Hi,

It is a curious inconsistency that INTEGERs overflow
quietly, but LONGINTs cause a TRAP.

ButI would not call it 'Wrong'; decisions have to be taken and
either choice is sometimes useful, sometimes undesirable.

Gardens Point CP, I believe, allows the option to switch this behaviour
on a
PROCEDURE by PROCEDURE basis, which would not be possible if the
behaviour was
specified in the language report, rather than being at the compiler
writer's
discretion.

The GP flexibility is GOOD because it allows more problems to be solved
concisely and efficiently; more 'power'.

The GP flexibility is BAD because you can't understand what the source
code
does by reading it alone, and it is harder to understand when you do
also read
the compiler options.


Regards

Robert

 

>> -----Original Message-----
>> From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
>> Of luowy{([at]})nowhere.xy
>> Sent: 06 April 2011 23:25
>> To: BLACKBOX{([at]})nowhere.xy
>> Subject: [BLACKBOX] INTEGER Add Has Wrong result
>>
>>
>> *** WARNING ***
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>> Keep this in mind if you answer this message.
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>>
>> look it:
>>
>> MODULE Test;
>> IMPORT StdLog;
>>
>> PROCEDURE Do*();
>> VAR i,j:INTEGER;l:LONGINT;
>> BEGIN
>> i:=MAX(INTEGER);(* 07FFFFFFH *)
>> j:

>> l:=i+j;(* l should be 080000000L *)
>> StdLog.Int(l);Log.Ln; (* ???? l:= -2147483648;
>> 0FFFFFFFF80000000L *)
>> END Do;
>>
>> END Test.
>>
>>
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Received on Thu Apr 07 2011 - 09:45:01 UTC