Re: Make sorting stable

On Fri, Mar 6, 2020 at 12:58 AM Andrea Faulds <ajf@ajf.me> wrote: > Hi, > > Nikita Popov wrote: > > > > I've implemented this variant now. If the comparison function returns a > > boolean, you get > > > >> Deprecated: usort(): Returning bool from comparison function is > > deprecated, return one of -1, 0 or 1 instead in %s on line %d > > > > once per usort() call, and we retry with swapped operands to ensure > > compatibility. > > > > Regards, > > Nikita > > > > I think that message could be a little misleading, because any negative > or positive value is valid, not just those of magnitude 1, right? IIRC > strcmp($a, $b) doesn't just return -1 and 1, and of course this is also > the case for the classic ($a - $b). > I've update the message to say: > Deprecated: usort(): Returning bool from comparison function is deprecated, return an integer less than, equal to, or larger than zero in %s on line %d The astute reader will notice that this is equivalent to "any integer", but I think phrased this way, the meaning should be clear to anyone familiar with the basic concept of comparison functions, while not mentioning -1, 0 and 1 in particular. Regards, Nikita PS: Yes, I'm aware that you can also return a floating point number. No, you should definitely not do that, because it's going to get casted to an integer and produce wrong results if the numbers get large enough.