[vcf-midatlantic] 2:00am BASIC epiphany

[Evan Koblentz]

>> of about being than just

That made perfect sense in my head last night. :)

On Fri, Aug 31, 2018, 2:30 AM Evan Koblentz <evan at vcfed.org> wrote:

> I had a spontaneous idea tonight for removing two lines of my Lego robot
> code.
>
> As usual, this epiphany on my part is probably TOTALLY FRIGGIN' OBVIOUS
> to most of you, but I'm proud that I figured it out on my own. :)
>
> Before, on the forklift robot, this was my code for checking the
> upper/lower touch sensors (limit switches) and moving the forklift motor
> appropriately. I had it at 9 lines (not counting REMarks) which was
> greatly reduced from Dan R.'s original 16 lines.
>
> 3010 IF PEEK (49249) > 127 AND PEEK(L) = 64 THEN RETURN
> 3020 IF PEEK (49249) > 127 THEN POKE L,16
> 3030 IF PEEK(L) = 80 THEN RETURN
> 3040 IF PEEK(49249) > 127 THEN GOTO 3020
> 3050 IF PEEK(49250) > 127 AND PEEK(L) = 128 THEN RETURN
> 3060 IF PEEK(49250) > 127 THEN POKE L,32
> 3070 IF PEEK(L) = 160 THEN RETURN
> 3080 IF PEEK(49250) > 127 THEN GOTO 3060
> 3090 RETURN
>
> Background: In that code, PEEK(49249) in Applesoft checks joystick
> button 0 and PEEK(49250) checks button 1. If their value is greater than
> 127 then you know they're currently being pressed. PEEK(L) checks the
> value at the address of the interface card. 64/128 are the sensors
> attached to ports (bits) 6 and 7, respectively. POKE L,16/32 turns on
> the motor (in opposite directions) that's attached via a connector
> spanned to ports 4/5. Lines 3030 and 3070 stop the motors if the sensors
> become active ** while ** the motor is moving, because then the total
> value being read from the interface box is sensor + the motor.
>
> The idea that popped into my head tonight: you can combine lines
> 3010/3020 into one, and also lines 3050/3060 into one, thereby reducing
> the routine by two lines and having the same effect.
>
> 3010 IF PEEK (49249) > 127 AND PEEK(L) <> 64 THEN POKE L,16
> 3020 IF PEEK(L) = 80 THEN RETURN
> 3030 IF PEEK(49249) > 127 THEN GOTO 3010
> 3040 IF PEEK(49250) > 127 AND PEEK(L) <> 128 POKE L,32
> 3050 IF PEEK(L) = 160 THEN RETURN
> 3060 IF PEEK(49250) > 127 THEN GOTO 3040
> 3070 RETURN
>
> So instead of saying, "Exit the routine if the lower/upper touch sensors
> are active, which we know is true if the value at address L is 64 or
> 128," instead I'm saying, "Turn on the motor ** ONLY IF ** the
> lower/upper touch sensors aren't active."
>
> I can't test it until this weekend at the soonest, but I am ** pretty
> sure ** it'll work -- or at least I don't see any obvious reason why it
> would ** not ** work. After all, the forklift motor can't turn on when
> either sensor is active, because I'm not programmatically allowing it --
> right?
>
> If it works, then I'll convert it to IBM BASIC too. The button PEEKs
> become STRIG (stick trigger) values, and the POKEs become OUT.
>
> Saving two lines of interpreted / non-compiled BASIC isn't going to have
> any significant impact on program execution speed or disk space, but it
> makes the code that much easier for non-programmers to understand, and
> it gives me that much more confidence of about being than just another
> English major. :)
>