digitalmars.D.bugs - [Issue 3232] New: std.math.approxEqual should consider maxAbsDiff when rhs==0 && lhs!=0
- d-bugmail puremagic.com (43/43) Aug 07 2009 http://d.puremagic.com/issues/show_bug.cgi?id=3232
- d-bugmail puremagic.com (6/6) Aug 11 2009 http://d.puremagic.com/issues/show_bug.cgi?id=3232
- d-bugmail puremagic.com (10/10) Oct 11 2009 http://d.puremagic.com/issues/show_bug.cgi?id=3232
- d-bugmail puremagic.com (12/12) Aug 27 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3232
http://d.puremagic.com/issues/show_bug.cgi?id=3232 Summary: std.math.approxEqual should consider maxAbsDiff when rhs==0 && lhs!=0 Product: D Version: 2.031 Platform: Other OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: Phobos AssignedTo: nobody puremagic.com ReportedBy: bugzilla kyllingen.net Currently, approxEqual doesn't take the maximum absolute difference into account when rhs is zero while lhs is nonzero. An example: double epsrel = 0.01; // ...or whatever, it doesn't matter double epsabs = 1e-5; // This matters when rhs or lhs is zero! assert (approxEqual(0.0, 1e-10, epsrel, epsabs)); // OK assert (approxEqual(1e-10, 0.0, epsrel, epsabs)); // Fails! This is very unintuitive -- I think the order of the "operands" shouldn't matter here. The offending piece of code is at line 3087 of std.math (rev. 1233): if (rhs == 0) { return (lhs == 0 ? 0 : 1) <= maxRelDiff; } This could be changed to: if (rhs == 0) { return (lhs == 0 ? 0 : 1) <= maxRelDiff || (maxAbsDiff != 0 && fabs(rhs-lhs) <= maxAbsDiff); } Another option, if abs(lhs-rhs)/rhs and abs(lhs-rhs)/lhs could be considered equally good definitions of the relative difference, would be this: if (rhs == 0) { if (lhs == 0) return true; // Switch lhs and rhs return approxEqual(rhs, lhs, maxRelDiff, maxAbsDiff); } I actually prefer this one, because the name "approxEqual" doesn't in any way imply that the order of its arguments matter. It should simply return true if lhs and rhs are approximately equal, regardless of which is which. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 07 2009
http://d.puremagic.com/issues/show_bug.cgi?id=3232 00:36:02 PDT --- I just realised the two solutions I suggested are exactly equivalent. :) -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 11 2009
http://d.puremagic.com/issues/show_bug.cgi?id=3232 Andrei Alexandrescu <andrei metalanguage.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED CC| |andrei metalanguage.com AssignedTo|nobody puremagic.com |andrei metalanguage.com -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 11 2009
http://d.puremagic.com/issues/show_bug.cgi?id=3232 Lars T. Kyllingstad <bugzilla kyllingen.net> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution| |FIXED 06:44:27 PDT --- Fixed by Andrei a long time ago. http://www.dsource.org/projects/phobos/changeset/1313 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 27 2010