https://bugzilla.novell.com/show_bug.cgi?id=361973
Summary: System.Random never returns smallest value if range is
negative
Product: Mono: Class Libraries
Version: unspecified
Platform: x86
OS/Version: Ubuntu
Status: NEW
Severity: Normal
Priority: P5 - None
Component: System
AssignedTo: mono-bugs@lists.ximian.com
ReportedBy: [EMAIL PROTECTED]
QAContact: mono-bugs@lists.ximian.com
Found By: ---
Description of Problem:
If one uses System.Random.Next(low, high) with a negative value for low, it
will never return low as the random sample.
Steps to reproduce the problem:
1. Call System.Random.Next(-1,1)
2. see that it always returns 0 (never -1 as it should do half the time).
Actual Results:
0 is returned.
Expected Results:
-1 approximately half the time, 0 approximately half the time.
How often does this happen?
every time.
Additional Information:
The bug is actually quite easy to fix. In System.Random there is a line in
Next(int, int) that looks like:
int result = (int)(Sample () * diff + minValue);
The problem is that (int) rounds towards zero. You really want Math.Floor,
which rounds towards negative infinity. If minValue is negative and Sample()
returns a number greater than zero (which it practically always will) result
will never equal minValue.
It should be:
int result = Math.Floor (Sample () * diff + minValue);
or cast the Sample () * diff to a uint first (since it must fit as the
difference of two ints), and the rounding towards zero in that case is correct.
int result = (int)((uint)(Sample () * diff) + minValue);
--
Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
You are the assignee for the bug.
_______________________________________________
mono-bugs maillist - mono-bugs@lists.ximian.com
http://lists.ximian.com/mailman/listinfo/mono-bugs
