From: DarthBob88 <darthbob88@gmail.com>
Subject: Re: "Constraint Error: Range Check" That Does Not Always Occur
Date: Thu, 22 Nov 2007 19:48:21 -0800 (PST)
Date: 2007-11-22T19:48:21-08:00 [thread overview]
Message-ID: <211e539c-81a8-4598-9acd-33907d03ad96@d4g2000prg.googlegroups.com> (raw)
In-Reply-To: uwssa4bbn.fsf@earthlink.net
On Nov 22, 6:14 am, Matthew Heaney <matthewjhea...@earthlink.net>
wrote:
> DarthBob88 <darthbo...@gmail.com> writes:
> > procedure test is
> > subtype Die is Integer range 1..6;
> > --Declare that anything of type Die may be
> > --an integer, value between 1 and 6, inclusive, and sod-all else.
>
> That's fine.
>
> > subtype Dice is Integer range 3*Die'First .. 3*Die'Last;
> > --Declares that Dice may be anything from 3 to 18.
>
> But you sum 4 dice; that's a min of 4 * 1 and a max of 4 * 6 -- why did you
> make your Dice subtype too small?
That would because I cut'n'pasted it from a program to simulate
rolling two dice. As for the 3 and 4 discrepancy, that's just
stupidity on my part. I was trying to simulate the sum of three dice,
chosen from four that were rolled. Hence, that little idiocy.
*facepalm*
> > package Random_Die is new Ada.Numerics.Discrete_Random (Die);
> > use Random_Die;
> > --Random generator; produces an integer between 1 and 6
>
> Right.
>
> > sum : Integer := 0;
> > G: Generator;
> > D1 : Dice;
> > D2 : Dice;
> > D3 : Dice;
> > D4 : Dice;
> > --Declare four Dice
>
> --or: D1, D2, D3, D4 : Die; -- DICE IS THE WRONG SUBTYPE
> -- Sum : Dice; -- subtype should be 4 .. 24
>
> > begin
> > Reset(G);
> > D1 := Random(G);
> > D2 := Random(G);
> > D3 := Random(G);
> > D4 := Random(G);
> > --I Haven't found the error just yet, but a Constraint_Error
> > --Occasionally comes up for the previous 4 lines
> > --I haven't been able to find it online, but I presume
> > --It's because the generator comes up with a number outside of [1,6]
>
> The generator will return you a random number between 1 and 6 (inclusive).
>
> Your Die subtype has a minimum bounds of 1, so the random number can (and will)
> return values that include the values 1 and 2.
>
> Your Dice subtype (to which you assign the value returned by the generator) has
> a minimum bound of 3. So when the random number generator returns a value less
> then 3, you get C_E during the assignment.
>
> Just change the declarations of Dx to use subtype Die instead of Dice, and then
> all is well.
Thank you kindly, sir. Ladies and gentlemen, this is why you should
not code at 0-dark-30, because you make idiotic mistakes like this,
instead of thinking through them.
> > sum := D1 + D2 + D3 + D4;
> > --Debugging
> > Ada.Integer_Text_IO.Put(D1);
> > Ada.Integer_Text_IO.Put(D2);
> > Ada.Integer_Text_IO.Put(D3);
> > Ada.Integer_Text_IO.Put(D4);
> > Ada.Integer_Text_IO.Put(sum);
> > end test;
> > --compile Ada programs with gnat make <foo>.adb
>
> > If it helps any, I'm using the Windows version of GNAT on XP. Thanks
> > in advance.
prev parent reply other threads:[~2007-11-23 3:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-22 6:42 "Constraint Error: Range Check" That Does Not Always Occur DarthBob88
2007-11-22 7:38 ` Damien Carbonne
2007-11-22 9:12 ` anon
2007-11-22 9:56 ` Stephen Leake
2007-11-26 18:38 ` Adam Beneschan
2007-11-22 9:47 ` Stuart
2007-11-22 14:14 ` Matthew Heaney
2007-11-23 3:48 ` DarthBob88 [this message]
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