3 ms·

They are not "technically equivalent", as I've shown above. You can implemnt papre/scissors/rock with [-1,0,1], which is not linear ordering function. And you

• afiori 5y ago
  > And you didn't show anything for which ordering cannot be defined by mapping objects (with any number of parameters) to strings, which is kind of the whole purpose of sortBy anyway I did so by intentionally, as i believe that mapping to complex enough strings is enough. > You can implemnt papre/scissors/rock with [-1,0,1], which is not linear ordering function. In PHP and in most other languages NaN == NaN, NaN === NaN, NaN <= NaN, and NaN < NaN are all false due to how IEEE floating point numbers are defined so you can have weird stuff going on there too. With some testing: $v=[1,2,3,4,5,6]; usort($v,$f); for: $f=function($a,$b){ return ($a - $b)%3; }; $f=function($a,$b){ return -($a - $b)%3; }; $f=function($a,$b){ return 1; }; $f=function($a,$b){ return -1; }; $f=function($a,$b){ return 0; }; it appears that once $f($a,$b) is calculated $f($b,$a) is inferred to be -$f($a,$b) and to guarantee $f($v[i],$v[i+1]) <= 0 under that assumption. But I am not sure... honestly i don't care... I am not arguing that one is better than the other...