About tcRunCycle()

When i read the source code in void tcRunCycle(TP_STRUCT *tp, TC_STRUCT *tc, double *v, int *on_final_decel) , I can't understand the follows mean:
discr = 0.5 * tc->cycle_time * tc->currentvel - (tc->target - tc->progress);
discr = 0.25 * pmSq(tc->cycle_time) - 2.0 / tc->maxaccel * discr;
newvel = maxnewvel = -0.5 * tc->maxaccel * tc->cycle_time +tc->maxaccel * pmSqrt(discr);
although i have read Simple Tp Notes(wiki.linuxcnc.org/emcinfo.pl?action=history&id=Simple_Tp_Notes), and understand it.
Is there anyone can explain it? or you can contact me with email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Thank you very much.

Yes. I think it is a basic question. Anyway thank you, i will try there.

But there is nobody reply it. I am still looking forward to anyone explain it to me here.
Thank you!

Anders Wallin have explained it on the mailing list. Thank him very much.Here it goes:http://www.anderswallin.net/2011/05/emc2-tpruncycle-revisited/

Chen Chengxi