3-bit flag

Discussion around the Swiss Micros DM42 calculator.
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firai
Posts: 27
Joined: Sun Sep 27, 2020 11:38 am
Location: NYC/HK

3-bit flag

Post by firai »

I'm probably getting too carried away with developing the menu system for this new program that I'm working on, but I want one of the sub-menus to show a • after the choice name if the user selected an option before and selected this particular option out of 4 (might be more for another building code). Does anyone have suggestions for smarter ways to go about this than my attempts below?

One of the ways I thought of doing this is with 3 flags:

Code: Select all

64 "d"
65 FC? 01
66 GTO d
67 FS? 02
68 FC? 03
69 GTO d
70 ├"•"
71▸LBL d
72 KEY 4 XEQ 16
73 MENU
...
93▸LBL 16
94 SF 01
95 SF 02
96 SF 03
97 RTN
But the code gets quite long and is marginally readable. Here's a slightly more readable variation with flags but with one more line per option:

Code: Select all

64 "d"
65 FC? 01
66 GTO d
67 FS? 02
68 GTO d
69 FS? 03
70 GTO d
71 ├"•"
72▸LBL d
73 KEY 4 XEQ 16
74 MENU
Using an actual variable to store the value in decimal form would be another option, but it would disrupt the stack unless I add even more code to restore the original values. It also doesn't seem to save as many lines of code as I thought it would, once I add the roll-downs after testing and setting the value.

Code: Select all

64 "d"
65 RCL a
66 4
67 X=Y?
68 ├"•"
69 R↓
70 R↓
71 KEY 4 XEQ 16
72 MENU
...
92▸LBL 16
93 4
94 STO a
95 R↓
96 RTN
Any ideas?

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Sam
whuyse
Posts: 84
Joined: Thu Dec 21, 2017 1:23 pm

Re: 3-bit flag

Post by whuyse »

I hope I have understood what it is you're trying to do..
If there are only 4 choices, and you want to show the dot for only one, why do you need three flags? Two will do?
Another way to avoid stack disruption is the use of ISG and DSE.
Suppose your choices are 0,1,2,3 - designate 0 to be the one that causes the dot to be shown.

Code: Select all

 "d"
 DSE a
 nop (any one-byte instruction as it is never executed)
 ISG a
 +"•"
 KEY 4 XEQ 16
The value of a is unchanged by the succession of DSE and ISG.

Cheers, Werner
42S #3249S01123
DM42 #00345
firai
Posts: 27
Joined: Sun Sep 27, 2020 11:38 am
Location: NYC/HK

Re: 3-bit flag

Post by firai »

Thanks for your response. The reason why I used 3 flags was because I wanted to show the dot only if the user has selected an option after starting the program. That is, there's a state "0" for the case where the user hasn't selected anything yet, resulting in a total of 5 possible states when there are 4 choices.

With the DSE+ISG technique, it seems like I can only store 2 possible states with each variable (≤0 and >0). Is my understanding correct? So I would still need to test and set 3 variables to allow 5 possible states, correct? Using this method of course would allow me to use the LSTO statement to declare "local flags", as your previous post mentioned.
Sam
whuyse
Posts: 84
Joined: Thu Dec 21, 2017 1:23 pm

Re: 3-bit flag

Post by whuyse »

-- UPDATE -- : the LBL 10 was misplaced of course, plus some initialisations added

okay, I think I understood now: you can only choose 1 option, A,B,C or D. And when you just entered, none have been chosen.
Choosing another option will erase the previously chosen one.

So, two options
1.with a variable a, initialised to 0

Code: Select all

 0
 STO a
 CLMENU
 
 LBL 10
 RCL a
 "A"
 DSE ST X
 X#0? @ nop
 X=0?
 +"."
 KEY 1 XEQ 01
 "B"
 DSE ST X
 X#0?
 X=0?
 +"."
 KEY 2 XEQ 02
 "C"
 DSE ST X
 X#0?
 X=0?
 +"."
 KEY 3 XEQ 03
 "D"
 DSE ST X
 X#0?
 X=0?
 +"."
 KEY 4 XEQ 04
 Rv
 MENU
 STOP
 GTO 10

 LBL 01
 1
 STO a
 Rv
 RTN
 LBL 02
 2
 STO a
 Rv
 RTN
 LBL 03
 3
 STO a
 Rv
 RTN
 LBL 04
 4
 STO a
 Rv
 RTN
2. with 5 (!) flags, all clear at the beginning:

Code: Select all

 CLMENU
 XEQ 00
 CF 00
 
 LBL 10
 "A"
 FS? 01
 +"."
 KEY 1 XEQ 01
 "B"
 FS? 02
 +"."
 KEY 2 XEQ 02
 "C"
 FS? 03
 +"."
 KEY 3 XEQ 03
 "D"
 FS? 04
 +"."
 KEY 4 XEQ 04
 MENU
 STOP
 GTO 10

 LBL 01
 XEQ 00
 SF 01
 RTN
 LBL 02
 XEQ 00
 SF 02
 RTN
 LBL 03
 XEQ 00
 SF 03
 RTN
 LBL 04
 XEQ 00
 SF 04
 RTN
 LBL 00
 SF 00
 CF 01
 CF 02
 CF 03
 CF 04
 RTN
In the latter case, perhaps flag 0 is not needed?
Cheers, Werner
42S #3249S01123
DM42 #00345
Dave Britten
Posts: 113
Joined: Wed Jun 14, 2017 9:27 pm

Re: 3-bit flag

Post by Dave Britten »

I would probably take the lazy way out: use 4 flags. :) Unless your program has maxed out the number of available flags, this sounds like premature optimization.

Have a LBL you can XEQ that simply clears all 4 flags and returns. Call this at the start of the program, and at the beginning of each of the four KEY GTO routines (followed by setting the flag the user has selected).

Code: Select all

LBL "MYPROG"
XEQ 15
LBL 00
CLMENU
"A"
FS? 01
|-"*"
KEY 1 GTO 01
"B"
FS? 02
|-"*"
KEY 2 GTO 02
...
MENU
STOP
GTO 00
...
LBL 01
XEQ 15
SF 01
GTO 00
...
LBL 15
CF 01
CF 02
CF 03
CF 04
RTN
firai
Posts: 27
Joined: Sun Sep 27, 2020 11:38 am
Location: NYC/HK

Re: 3-bit flag

Post by firai »

Thanks Werner and Dave! I was indeed trying to compact the storage too much, resulting in more memory required for the extra instructions than the one flag (that I didn't save because the flag exists anyway). Using 4 flags seems like the way to go.

Werner, flag 00 is represented by flag clear for all for the other 4 flags and indeed not necessary. The sequential DSE is quite clever; I'm going to keep that in my library of code snippets. Might come in handy in the future.
Sam
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