random numbers in pbasic?

Rontopia

Im still new to basic so let me discribe my issue.

I have a boebot that is roaming with a sonic sensor. I wrote all this code myself and its working quite well. when this program is done I will post it here for others to look at and give feedback on.

right now, my bot goes forward with the sonic sensor pinging away. every so often, the bot stops and the the sonic sensor pings in 3 different directions and saves the values. depending on what those values are the bot turns and gos on its way..

so there is a value in 3 drections but if there is an object in the forward direction and nothing to the sides.. ie· 0 1 0 .. I have the bot truning to the 15 degrees·right and starting forward on its way again. what i would like to happen is.. the the case of 0 1 0.. I would like a random 50/50 chance to trun right or left.. and contunue on its way..

problem is I have no idea how to do this in pbasic. I understand how and where I need to branch and return to.. but as far as the random 50/50 chance im clueless. I am assuming that I need some kind of counter or something but how to stop it randomly is the real quesion? after that its simple evaluation to get to the result..

anyway.. does anyone have any ideas or pointers?

thanks for your time



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Muahdib


IC layout designer
Phoenix Arizona

Post Edited (Muahdib) : 12/6/2006 4:20:42 PM GMT

Phil Pilgrim (PhiPi)

Take a look at PBASIC's RANDOM operator. You can then "flip a coin" by determining whether the random variable is greater than 32767 or not.

-Phil

Rontopia

ok.. sorry, I actually went and did some reading and found that there is a random key word.. its that nice[noparse]:)[/noparse] but I am having trouble with syntax.. so for any help I would be most thankful

so tell me if there is anything wrong with this bit of code

Randomnum:
IF counter2 > 14 THEN
counter = 0
counter2 = rvalue
ENDIF

RANDOM rvalue
counter2 = counter2 + 1
IF rvalue > 32767 THEN
GOSUB TurnR
ELSE
GOSUB TurnL
ENDIF
RETURN



I have made 2 varibles one is a nib and one is a word. Im using the nib to count from 0 to 14 . making that value the seed value

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Muahdib


IC layout designer
Phoenix Arizona

Rontopia

opps its actually counting 0 to 15.. my bad.

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Muahdib


IC layout designer
Phoenix Arizona

Rontopia

and that 2nd counter should be counter2.. im at work guys and I got so much going on that I cant focus, if you cant tell by my posts..

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Muahdib


IC layout designer
Phoenix Arizona

Zoot

Since random numbers are only "pseudo-random" on the Stamp, you might want to seed your random call with a number that changes a lot -- randomly. I often use one of my sensor values and maybe a counter too -- your sonar sensor will be returning slightly different values all the time and can make a decent pseudo random seed.

someSensor  VAR  Word    'some changing value ---
work             VAR  Word     'work for random (16 bit)
counter         VAR   Word   'or byte or nib or any counter or index in your program that changes a lot

RandomDir:
   GOSUB Get_Rand    'this subroutine returns work as a 16 bit random number
   IF work.BIT0 = 0 THEN     'just use bit0 -- the number has to be even or odd
       GOSUB TurnL
    ELSE
       GOSUB TurnR
    ENDIF
    RETURN

Get_Rand:         'nice to have a standalone random number generator for all kinds of things
    work = SomeSensor*counter   'or other "seed value" that changes often during other operations in your program
    RANDOM work
    RETURN

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When the going gets weird, the weird turn pro. -- HST

Rontopia

your right.. the code I wrote there will trun left then right then left then right.. the reason I did it this way is so that I only want to use 1 word varable because ram is so limited. but I think I can work with your idea. I dont understand the work.BIT0 statement? .BIT0 refers to what bit?


thanks.. for the input..

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Muahdib


IC layout designer
Phoenix Arizona

Zoot

Bits are numbered 0 - 15 in a Word and 0 - 7 in a Byte, etc., with 0 being the right-most or (L)east (S)ignificant (B)it and -- in this case -- 15 being the left-most or (M)ost (S)ignificant (B)it.

So grabbing BIT0 is the same as saying Value//2. BIT0 will be 0 if the number is even and 1 if the number is odd, in other words. Now, for your particular random scenario, you could actually grab *any* bit.

You could also do something similar with a lookup table, or an ON statement, whatever:

RandomTurn:
RANDOM work 'some random value
ON work.BIT0 GOSUB TurnL, TurnR
RETURN

TurnL:
'some left turn code that you can use all over your program
RETURN

TurnR:
'some right turn code -- ditto
RETURN

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When the going gets weird, the weird turn pro. -- HST

Post Edited (Zoot) : 12/7/2006 1:55:18 PM GMT

AIman

The way I did random numbers was to use numbers I wouldn't know. The first was equal to my encoder / lapsed seconds and the second was seeded with the first. So in english it goes like this

Random generator = (time in seconds/encoder wheel count)*2
if random generator is even then turn left
if random generator is odd the turn right

Zoot

AIman is doing something similar to what I suggested -- use a value that is a constantly used and changing variable for your seed -- a sensor input, a program counter, an encoder, whatever.

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When the going gets weird, the weird turn pro. -- HST

Rontopia

wow thanks guys.. thats just to cool. I think I got it now.. well almost but I think I know enough to be dangerous[noparse]:)[/noparse]

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Muahdib


IC layout designer
Phoenix Arizona