(42S) GCF

07102016, 04:41 AM
(This post was last modified: 06152017 01:48 PM by Gene.)
Post: #1




(42S) GCF
Prompted by Eddie W Shore's
http://www.hpmuseum.org/forum/thread6528.html here's my short GCD programme. The prog takes X & Y values from stack & returns GCD , or GCF if you wish, to stack level X. Code:


07102016, 07:21 AM
Post: #2




RE: HP 42S: GCF
Same as mine, except I have a "+" in step 8 (since you know X contains zero).
I also add Smallest Common Multiple: *LBL "SCM" RCL ST Y RCL ST Y XEQ 00 / x RTN Cheers, Werner 

07102016, 08:41 PM
Post: #3




RE: HP 42S: GCF
Is this ABS necessary?
Günter 

07112016, 04:26 AM
Post: #4




RE: HP 42S: GCF
Yes, ABS is needed for some negative inputs, otherwise the GCD is returned as a negative which is surely not the GREATEST common factor.


07112016, 09:15 AM
Post: #5




RE: HP 42S: GCF  
07112016, 10:01 AM
Post: #6




RE: HP 42S: GCF
Look at your own code ;)
it does GCF, I keep them both in 1 program. Werner 

07112016, 06:58 PM
(This post was last modified: 07112016 07:11 PM by Dieter.)
Post: #7




RE: HP 42S: GCF
(07102016 04:41 AM)Gerald H Wrote: here's my short GCD programme. Fine – my fractions programs used virtually the same code, but with a final + instead of R↓ which works as a DROP here. ;) FTR, here is an alternate GCD routine with a slightly shorter and thus faster loop. It can be used if Z does not have to be preserved: Code: 01 LBL 00 And finally a solution that returns both LCM and GCD (in Y resp. X): Code: 01 LBL"LCMGCD" This is HP41 code. HP42s users may imagine an additional "ST" in the stack related commands. ;) Dieter 

07122016, 04:46 AM
Post: #8




RE: HP 42S: GCF
(07112016 06:58 PM)Dieter Wrote:(07102016 04:41 AM)Gerald H Wrote: here's my short GCD programme. I tried the first programme but for various inputs it returned 1. 

07122016, 04:59 AM
Post: #9




RE: HP 42S: GCF
Sorry, my error, I entered STO "Z" for STO ST Z.
Now functions correctly. 

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