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Prime Factors
05-18-2015, 06:10 PM (This post was last modified: 05-19-2015 01:13 PM by Dave Britten.)
Post: #1
Prime Factors
In an attempt to rival Doom for the largest number of systems to which it's been ported, here's the usual HP 67 "mod 30" prime factors program for the 41C/CV/CX.

Enter a positive integer, and XEQ FCTR. Press R/S to view each factor. Zero will be displayed when there are no more factors.

Note this is a pretty straight port, and hasn't been fancied up with any 41-specific capabilities (yet).

EDIT: Here's a slightly improved version with a couple optimizations, and multiplicity display for factors (e.g. 3^2, 7^3, etc).

Code:
01 LBL FCTR
02 CF 05
03 FIX 0
04 STO 00
05 SQRT
06 STO 01
07 0
08 STO 02
09 STO 03
10 2
11 XEQ 02
12 1
13 XEQ 02
14 2
15 XEQ 02
16 2
17 XEQ 02
18 RCL 00
19 1
20 X=Y?
21 GTO 09

22 LBL 01
23 4
24 XEQ 02
25 2
26 XEQ 02
27 4
28 XEQ 02
29 2
30 XEQ 02
31 4
32 XEQ 02
33 6
34 XEQ 02
35 2
36 XEQ 02
37 6
38 XEQ 02
39 RCL 00
40 1
41 X=Y?
42 GTO 09
43 RCL 01
44 RCL 02
45 X<=Y?
46 GTO 01
47 RCL 00
48 STO 02
49 0
50 XEQ 02
51 GTO 09

52 LBL 02
53 ST+ 02
54 RCL 00
55 RCL 02
56 MOD
57 X!=0?
58 GTO 05

59 LBL 03
60 RCL 02
61 ST/ 00
62 RCL 00
63 SQRT
64 STO 01
65 1
66 ST+ 03
67 SF 05
68 0
69 GTO 02

70 LBL 05
71 FC?C 05
72 RTN
73 RCL 03
74 RCL 02
75 CLA
76 ARCL X
77 |-^
78 ARCL Y
79 0
80 STO 03
81 PROMPT
82 RTN

83 LBL 09
84 CLX
85 RTN
86 END
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05-18-2015, 08:31 PM
Post: #2
RE: Prime Factors
(05-18-2015 06:10 PM)Dave Britten Wrote:  Note this is a pretty straight port, and hasn't been fancied up with any 41-specific capabilities (yet).

You might have a look at a program for the HP-42s which uses the same idea.

Cheers
Thomas
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05-19-2015, 02:58 AM
Post: #3
RE: Prime Factors
(05-18-2015 08:31 PM)Thomas Klemm Wrote:  
(05-18-2015 06:10 PM)Dave Britten Wrote:  Note this is a pretty straight port, and hasn't been fancied up with any 41-specific capabilities (yet).

You might have a look at a program for the HP-42s which uses the same idea.

Cheers
Thomas

Thanks Thomas. Clever use of t-copy there. I see a couple things that could be issues for a 41 port: the use of recall arithmetic, as mentioned in that thread, AIP, which requires the appropriate module or alternative code, and the alpha register being limited to 24 characters. I don't recall the 42S alpha limit, but I think I remember it being larger.

I changed my version a bit to display multiplicity of factors as they're found (3^2, 5^3, etc.) and also replaced the / FRC bits with MOD, which appears to be about 20% faster. I'll probably post the updated code tomorrow.
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