Hello there,

Is anyone able to tell me why my little bit of code just returns:

[NIL]
[NIL]
[NIL]
[NIL]
...and so on?

I thought maybe I had to manually return something from the function, but I understand all values are global unless declared local - is that right? I thought maybe forcing it into a string with TOSTR might work, but no.

I'm not sure where to go from here.

function _init()
    createtable()
end

function _update()
    pickrandomteam()
end

function _draw()
    print(randteam)
end

-- user functions

function createtable()
    team={"liverpool","welling utd","arsenal","accrington stanley"}
end

function pickrandomteam()
    n=rnd(3)
    randteam=team[n]
end

D'oh!

Just found the answer - I'm assuming the random number generator produce decimals unless you FLR it.

FLR(RND(3))

Hi Pico Noob! You are correct about needing to use flr, however lua arrays are one indexed and rnd gets a number from 0 so you actually need
flr(rnd(3))+1
On top of that, there is a # key in lua that gets the number of items in a table, so you could use
flr(rnd (#team))+1
So then you could add and take away entries from team and this line of code would scale to compensate.

In fact, it's often useful to have a little function that does exactly that, all in one place:

function trnd(t)
  return t[flr(rnd(#t))+1]
end

color=trnd(palette)
player=trnd(team)
page=trnd(book)
etc.

Note that since array indices usually start at 1, picking a random item can be made a bit simpler by using ceil instead of flr, like so:

function randomitem(xs)
 return xs[ceil(rnd(#xs))]
end

As @Felice has pointed out to me before, while it looks like you're saving a token you have to remember that rnd(1) would return between 0 and 0.99999 (or some decimal around there). So doing this method leaves the (very very slim) chance of rnd returning 0, then ceil 0 returns 0 and trying to access element at index 0 causing a nil return.

If you're not worried about space, here is a robust random function I use in all my code that needs a random operator. It can be used three ways:

a=fnr(nn)

Gives you a random number zero to nn minus one.
a=fnr(8) : 0..1..2..3..4..5..6..7

a=fnr(n1,n2)

Gives you a random number from n1 to n2.
a=fnr(2,6) : 2..3..4..5..6

Reversing numbers also gets you the same results.
a=fnr(6,2) : 2..3..4..5..6

Negative numbers are also allowed.
a=fnr(-3,3) : -3..-2..-1..0..1..2..3

If you're curious about that a=b,b=a that idea comes from Felice. A good way to swap variables without using a 3rd.

As the results are always integer, you don't need to worry about floating point numbers, the decimal place, or returning non-integer values for integer arrays.

-- get random # ---------------
function fnr(a,b)
  if (b==nil) return flr(rnd(a))
  if (a>b) a,b=b,a
  return a+flr(rnd(b-a+1))
end--fnrr(..)

Davbo: good point about ceil(0)!

Thanks, folks. Helpful stuff.