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From: tmoran@bix.com (Tom Moran)
Subject: Re: Unreferenced lock variables
Date: 1999/04/20
Message-ID: <371cadb6.1137490@news.pacbell.net>#1/1
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Newsgroups: comp.lang.ada
Date: 1999-04-20T00:00:00+00:00
List-Id: <comp.lang.ada>

>> procedure Something(P : in integer) is
>>   Unused : integer := P/0;
>> begin ...

>> which can legally have Unused eliminated and thus the
>> divide by zero eliminated.  That certainly provides an
>> analogous precedent for eliminating the controlled
>> Initialize/Finalize.

>This is a bad analogy.
How about
type Back_Track_Type is array(integer range <>) of integer; 
function Big_Calculation(Distance:in integer; Time:in integer; ...)
return Back_Track_Type is  
   Speed : integer := Distance/Time;
   Where_it_was : Back_Track_Type(1 .. Time);
begin
   -- various calculations, some of which assume that the speed is
non-zero, but none of which actually mentions the variable "Speed"
  Granted, this would be poor programming, but the Distance/Time
calculation would give a divide by zero at the start of
Big_Calculation, while optimizing it away might result in erroneous
calculations that wouldn't show up till much later, in some other
place when it is surprisingly discovered that the back_track array
returned from the function was in fact null.  It seems to me that's a
closer analogy in terms of the difference in program behavior.