On 12 Aug 2014, at 15:01, Keary Suska <cocoa-...@esoteritech.com> wrote:
> > On Aug 12, 2014, at 1:42 AM, Dave <d...@looktowindward.com> wrote: > >>> Maybe my brain isn't working correctly but that doesn't make sense to me. >>> Could you show the output with both x and y shown? Now, you aren't dividing >>> by a negative integer, are you? I believe that is undefined… > > Yes, it's my brain. I just needed to see it to make sense of it. > >> I’m not doing any division, the function for “myMod” is as I posted: > > Well, it is the divisor I was asking about and although you aren't interested > in the quotient, you are asking for division to occur. > >> If you think of the number as being used as an Index into an NSArray, you >> can see why a true mod function is better, e.g. -1 gets you the last >> element, -2 the second from last and so on. > > I see that you are interested in a circular index. Most of the time I find > myself needing a "remainder" result more than a true modulo, so I use abs(). > That definitely won't work when you need the true series. Yes, this is what this thread is about. % was wrongly given the description of the modulus function in the 1960s/1970s and as a result of that one mis-naming “%” in C has been thought as a Modulus operation by a lot of people ever since (and it continues to be mis-described to this very day). The “%” character means a “remainder” not a “Modulus”, but are useful, but in this case I really wanted modulus. Most of the time remainder and modulus are the same thing, but when you introduce negative numbers remainder becomes a mirror image of the positive domain, where as modulus stays the same. I’m not sure what you mean by dividing by a negative number is undefined? It seems to work ok for what I’m doing in another place: NSInteger myIndex; CGPoint myStartPoint; CGSize mySize; myStartPoint = -640; mySize.width = 320; myIndex = myStartPoint.x / mySize.width; myIndex = -2 as expected. Is that what you meant? Dave _______________________________________________ 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
