algorithm - php 中的黑客新闻算法？

Question

这是 Hacker News 排名算法，我认为这是一种简单的排名方式，特别是如果用户对项目进行投票，但我真的不明白这个，可以将其转换为 PHP，所以我可以完全理解它？

; Votes divided by the age in hours to the gravityth power.
; Would be interesting to scale gravity in a slider.


(= gravity* 1.8 timebase* 120 front-threshold* 1
           nourl-factor* .4 lightweight-factor* .17 gag-factor* .1)

        (def frontpage-rank (s (o scorefn realscore) (o gravity gravity*))
          (* (/ (let base (- (scorefn s) 1)
                  (if (> base 0) (expt base .8) base))
                (expt (/ (+ (item-age s) timebase*) 60) gravity))
             (if (no (in s!type 'story 'poll))  .8
                 (blank s!url)                  nourl-factor*
                 (mem 'bury s!keys)             .001
                                                (* (contro-factor s)
                                                   (if (mem 'gag s!keys)
                                                        gag-factor*
                                                       (lightweight s)
                                                        lightweight-factor*
                                                       1)))))

Answer 1

直接从http://amix.dk/blog/post/19574并从 Python 翻译成 PHP:

function calculate_score($votes, $item_hour_age, $gravity=1.8){
    return ($votes - 1) / pow(($item_hour_age+2), $gravity);
}