RPL exercise - Last Digits of Primes (HP 49G, G+, 50g)
06-01-2019, 03:17 PM
Post: #11
 Gerson W. Barbosa Senior Member Posts: 1,603 Joined: Dec 2013
RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g)
(06-01-2019 08:51 AM)Carsen Wrote:  Hi Everyone.

Here's my take on the challenge. The algorithm is very straightforward. Get the next prime number, put it in a string, retrieve the last digit in the string, test if the digit is a 1, 3, 7, 9, or none of the above, & then add it to the list.

Code:
 <<   { 0 0 0 0 }  5 ROT 1 SWAP START NEXTPRIME DUP ->STR DUP SIZE DUP SUB STR-> CASE DUP 1 == THEN { 1 0 0 0 } END DUP 3 == THEN { 0 1 0 0 } END DUP 7 == THEN { 0 0 1 0 } END DUP 9 == THEN { 0 0 0 1 } END DUP == THEN { 0 0 0 0 } END END NIP ROT ADD SWAP NEXT DROP >>

Not great performance in Exact mode, hitting 151.9 seconds with 1000 primes starting with 7. However, in Approx. mode, I get a decent time of 86.5 seconds.

Thanks for the challenge Gerson. I had fun.

I am glad you had fun. That was the idea, hence an 'exercise', not a 'challenge'.

Just two remarks:

1) The STR-> before should be an OBJ-> (just a manual listing mistake);

2) You can omit the optional case clause, DUP == THEN { 0 0 0 0 } END (see grsbanks's comment below in this thread). Thus your byte count will be under 200 and you can save about three seconds in Exact Mode.

I had considered testing this CASE structure, but I didn't. Thanks for doing it. I would get about the same running times, but at least I could have tried Approximate Mode, which is not possible in my programs.

Gerson.
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 Messages In This Thread RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 03:07 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Valentin Albillo - 06-01-2019, 04:13 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 04:43 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - DavidM - 06-01-2019, 05:02 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gilles - 06-01-2019, 05:29 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Albert Chan - 06-01-2019, 12:42 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 05:44 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Carsen - 06-01-2019, 08:51 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - grsbanks - 06-01-2019, 12:48 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Valentin Albillo - 06-01-2019, 02:38 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 03:29 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Valentin Albillo - 06-01-2019, 09:59 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-02-2019, 10:43 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Valentin Albillo - 06-02-2019, 11:27 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-03-2019, 12:14 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Valentin Albillo - 06-03-2019, 04:25 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019 03:17 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 03:41 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - DavidM - 06-01-2019, 04:08 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-01-2019, 09:11 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Dave Britten - 06-01-2019, 11:05 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-02-2019, 06:10 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - John Keith - 06-02-2019, 04:39 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gilles - 06-02-2019, 09:18 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Carsen - 06-03-2019, 03:49 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-03-2019, 01:08 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Carsen - 06-03-2019, 08:15 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - Gerson W. Barbosa - 06-04-2019, 03:00 AM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - fred_76 - 06-04-2019, 02:21 PM RE: RPL exercise - Last Digits of Primes (HP 49G, G+, 50g) - ttw - 06-04-2019, 05:09 PM

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