From: tmoran@bix.com (Tom Moran)
Subject: Re: Unreferenced lock variables
Date: 1999/04/20
Date: 1999-04-20T00:00:00+00:00 [thread overview]
Message-ID: <371cadb6.1137490@news.pacbell.net> (raw)
In-Reply-To: 7fi0uj$k99$1@nnrp1.dejanews.com
>> 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.
next prev parent reply other threads:[~1999-04-20 0:00 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-04-11 0:00 Unreferenced lock variables Simon Wright
1999-04-11 0:00 ` Tom Moran
1999-04-12 0:00 ` Robert Dewar
1999-04-12 0:00 ` Simon Wright
1999-04-12 0:00 ` Robert Dewar
1999-04-12 0:00 ` Simon Wright
1999-04-14 0:00 ` Robert Dewar
1999-04-12 0:00 ` Jean-Pierre Rosen
1999-04-12 0:00 ` Simon Wright
1999-04-13 0:00 ` Robert Dewar
1999-04-13 0:00 ` Robert Dewar
1999-04-13 0:00 ` Tom Moran
1999-04-15 0:00 ` Robert Dewar
1999-04-15 0:00 ` Tom Moran
1999-04-16 0:00 ` Robert Dewar
1999-04-16 0:00 ` Tom Moran
1999-04-16 0:00 ` Tucker Taft
1999-04-16 0:00 ` Tom Moran
1999-04-19 0:00 ` Tucker Taft
1999-04-16 0:00 ` Tom Moran
1999-04-20 0:00 ` Tom Moran
1999-04-20 0:00 ` Robert Dewar
1999-04-20 0:00 ` Tom Moran [this message]
1999-04-21 0:00 ` Robert Dewar
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