From: Keith Boruff <kboruff@optonline.net>
Subject: Should be getting a constraint error in this code
Date: Sat, 24 Jul 2004 02:32:44 GMT
Date: 2004-07-24T02:32:44+00:00 [thread overview]
Message-ID: <gTjMc.2800$q9.4134490@news4.srv.hcvlny.cv.net> (raw)
Hey all,
Forgive me for posting such a trivial problem here but I couldn't seem
to find an answer in any of the FAQs I know of nor DejaNews.
Though I'm not a novice programmer, I am a novice Ada programmer.
In my studies this evening, I wrote the following trivial program to
force a constraint error:
with Ada.Text_Io; use Ada.Text_Io;
procedure Constraint_Tests is
type Exam_Mark is range 0 .. 100;
English : Exam_Mark := 72;
Math : Exam_Mark := 68;
Computing : Exam_Mark := 76;
Average : Exam_Mark;
begin
Put("Average exam mark is ");
-- I expect a constraint exception in this statement
-- because English + Math + Computing > 100
-- NOTE: On my machine, Exam_Mark'Base'Last = 127
Average := (English + Math + Computing) / 3;
Put_line(Exam_Mark'Image(Average));
end Constraint_Tests;
Ok, the problem I'm having is that I'm expecting a constraint exception
to occur because (English + Math + Computing) = 216 and the largest
value of its base is 127 (on my machine).
However, I'm not getting this at all. I get no constraint errors
whatsoever and what's worse, Average = 243. First of all, why didn't I
get a constraint error here (since Average is of type Exam_Mark)?
Secondly, where in the heck did 243 come from?
Now, if I omit the statement in the code and instead write:
Average := English + Math + Computing;
I get a constraint error as expected. When I use the '/' operator
though, all bets are off.
Is there something I'm not seeing here? Is there something about the /
operator I should know about?
Or... could this possibly be a bug in the compiler itself (using GNAT)?
I'm embarrassed to be posting such a trivial program but it really
bothers me that the behavior is not what I expect.
If anyone has any suggestions, I'd appreciate some info on the matter...
even if it's to tell me to RTFM (... as long as you provide a link).
Thanks,
Keith Boruff
next reply other threads:[~2004-07-24 2:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-24 2:32 Keith Boruff [this message]
2004-07-24 3:33 ` Should be getting a constraint error in this code Robert I. Eachus
2004-07-24 3:35 ` John B. Matthews
2004-07-24 15:08 ` Björn Persson
2004-07-25 13:54 ` Martin Krischik
2004-07-25 15:14 ` Nick Roberts
-- strict thread matches above, loose matches on Subject: below --
2004-07-26 6:42 Christoph Karl Walter Grein
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