Need a source of random numbers for Spin programs!

Dennis Ferron

I'm working on a Nibbles game for the Propeller and I can't seem to get any randomness to my computer-controlled snakes. Basically the "artificial stupidity" algorithm that controls the computer player is, when confronted by a situation where a collision will happen soon, try random turns until you escape or you die. But I can't find any random number function in the PropTool library so my snakes end up either in infinite loops because they never take a wrong turn or die because they can't think of a new set of turns.

Has anyone got a good random number object for the Propeller? If not, I'll write one and post it.

Bill Henning

Try a variation of an old standby:

last = cnt & 4095
prime = large 16 bit prime
another = another large 16 bit prime
...


prnd = (last * prime + another) & 65535
last=prnd

Phil Pilgrim (PhiPi)

You could use Spin's random operator, "?".

potatohead

Grab a seed from the system counter, when the user hits start. That way, they pick their own seed and you no longer worry about it. For a given seed, the spin operator will output the same set of random numbers. This can be very cool for game stuff, if you need repeatable randomness...

Assign it to a variable, called seed, rand, etc...

Use this seed in your AS [noparse]:)[/noparse] code

some_game_variable := seed?

Grab another seed, upon start, or on other user input, depending on your needs.

The string of random numbers generated is repeatable backward and forward.

If you say:

var := seed?, then you get one set of numbers.

If you say:

var := ?seed, then you get another set of numbers.

The difference is basically when the variable seed, gets put into the random operator. Pre or post.

Post Edited (potatohead) : 11/29/2006 7:42:53 AM GMT

Dennis Ferron

A random operator. I should have RTFM!

Chris Merck

Even after I knew about the "?" operator I had a little trouble with it. I did finally get it to work for my rogue game, here was the result:

VAR
long byte

PUB random_byte : retval
retval := ||(dice?//256)

PUB roll(number_of_dice, number_of_sides) : retval
retval := 0
repeat number_of_dice
retval += ||(dice?//number_of_sides) + 1

Chris Merck

of course the line after repeat is indented!

simonl

Hi Dennis,

Chip Gracey came up with a real random number generator here: http://forums.parallax.com/showthread.php?p=639978

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Cheers,

Simon

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