If that happens, it's a bug in the player. From the docs: "Returns a pseudo-random number n, where 0 <= n < 1. "
So, the biggest number random returns can approximate 1, but should never be 1. What I got wrong in my original answer was that multiplying by 2 and then rounding introduces a bias towards 1 (and then if you substract 1, the bias is towards 0). Think about it this way: You've got a number between 0 and 1.99999 when you do Math.random * 2. That is, a number that can get very close to 2, but never be actually 2. If you round it you'll get: 0 for 0...0.49 1 for 0.5...1.49 2 for 1.5...19 The actual numbers might not be exact as I'm not sure what's the boundary for rounding up or down; I'm also considering only two decimals for simplicity. But anyway, the distribution is obviously not even. There's about a 0.25 chance of getting 0, the same chance of getting 2, but the double, 0.5, of getting 1. However, if you multiply by 3 and floor the result (or coerce it to int for that matter), you get rid of the bias: Math.random * 3 will give a number in the range 0...2.99 So, if you get rid of the decimal part, you have: 0 for 0...0.99 1 for 1...1.99 2 for 2...2.99 Which gives a result that's clearly more evenly distributed than the first approach. 2010/5/9 Steven Sacks <[email protected]> > In the exception that Math.random() returns 1, in which case you would get > 2. > > I don't use Math.random(), though, I use the Parker-Miller PRNG. > > > > > On 5/9/2010 5:01 PM, Juan Pablo Califano wrote: > >> PS 2: I think the correct way to write the function that returns a number >> in >> the range -1 / 1 is: >> >> Math.floor(Math.random * 3) - 1 >> >> In this case, you could indeed use int() instead of a static Math method, >> so >> I guess I was wrong about your function needing a Math.round call. >> > _______________________________________________ > Flashcoders mailing list > [email protected] > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders > _______________________________________________ Flashcoders mailing list [email protected] http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
