35s - fun algebraic tricks #2 - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: 35s - fun algebraic tricks #2 (/thread-118349.html) 35s - fun algebraic tricks #2 - Gene Wright - 07-13-2007 Here's another type of fun algebraic trick that can be used in **RPN** programs. Suppose you have a 3-digit positive number in X and you want to determine the "sum of the digits" of the number. The program below will do this and not destroy the stack! LBL A press EQN RDMR(REGX,10)+RMDR(IDIV(REGX,10),10)+RMDR(IDIV(REGX,100),10) RTN The original stack is pushed to Y, Z and T. If you want to save Y, Z and T instead, then do a RDN after LBL A and change the RMDR line to point at REGT rather than REGX). 69 bytes used, but very handy to preserve the stack. I personally think these types of features will be very powerful in future programs. RMDR is the remainder function, IDIV is integer division, and REGX is the way the 35s refers to the value in register X. REGT would point at the value in the T register. When a function (like RMDR and IDIV) are presented in an algebraic context, it prompts the function name along with the open/close parentheses and a comma supplied (if needed to separate two arguments). To move across the comma to enter the second argument, you press the right arrow key. It's not hard to get used to at all. I'd better stop or this will be yet another learning module. Gene Re: 35s - fun algebraic tricks #2 - Les Wright - 07-13-2007 Gee, this is becoming a regular Nerds Anonymous meeting, isn't it? ;) Even better ... - Don Shepherd - 07-13-2007 sigma(i:0:log(n):1:mod(idiv(n:10^i):10)) Works for any length number. Re: Even better ... - Bruce Bergman - 07-13-2007 Don, I just KNEW I'd see you here in this thread. :-) :-) thanks, bruce Re: Even better ... - Gene Wright - 07-13-2007 Hmm. Sigma doesn't seem to work on the 35s in equation mode. :-) Wish it DID, but... Re: Even better ... - Bruce Bergman - 07-13-2007 What? I thought the 35s had the full solver functionality? Is that not true? Or has it been brain-downed? thanks, bruce Re: Even better ... - Don Shepherd - 07-15-2007 Bruce, I notice that Sigma is not available in the 33s, which is probably why it is not in the 35s.