I need to run some code only 40% of the times, how may i do this?

Question

[Rails] I need to run some code only 40% of the times, how may i do this?

i need to make some square items, and there can be a max of 5 per row, and a min of 1 per row. then i want to have a row with 2 boxes, 5boxe, 1 box and so on, random... the last box of the row, will have a clear:both class..

Answer 1

Generate a random number between 0.0 and 1.0 for instance and check if it's less than or equal to 0.4.

Answer 2

If you need to ensure that your task is run 4 out of 10 times then use this method:

some_task if run?

def run?()
 @i=(@i||0) + 1
 (@i-1)%10 < 4
end

Caveat:

You need to run the task at least 10 times to get the 40% distribution.
Distribution is not random