I usually use fabs() and compare to some small number for things like this, it explicitly says what your tolerance for 'same' is and if your points are going through a series of calculations, it's easy to get them to differ in the lower order bits however you cast them.
On 30-Jun-2010, at 4:35 PM, Rimas M. wrote: > Hello, > > I am stuck with floats (doubles, to be precise) comparison. > In part of my app, I am dealing with NSPoint components (x, y) > comparison. On 32bit architecture NSPoint components are floats, and > direct comparison ( float1 == float2 ) works fine. But on 64bit, they > are doubles and '==' does not work due to precision. > > Lets take an example: C and D are NSPoints. Lets say C is > (1.000000000000000444089209850063, whatever) and D is > (1.000000000000000000000000000000, whatever). > If my code is: if (C.x == D.x) thenDoSomething; , then thenDoSomething > is not called. Of course. > > But on my needs, float is more than enough for precision. > > So question is, what is the most efficient (performance side) and > simplest (coding side) way to compare those bastards? > > At the moment I am thinking about: > > a) BOOL _floatsOrDoublesAreEqual = ( (float)C.x == (float)D.x); > > b) BOOL _floatsOrDoublesAreEqual = ( fabs(C.x - D.x) <= _epsilon ); , > where _epsilon is something like 0.0001. > > Regards, > > Rimas M. > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/cocoa-dev/rols%40rols.org > > This email sent to r...@rols.org _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
