random
random integers
rand(1..5)
#=> one of 1, 2, 3, 4, 5
rand(1...5)
#=> one of 1, 2, 3, 4
rand(5)
#=> one of 0, 1, 2, 3, 4
#random floats
rand(5.0)
#=> one of integers 0, 1, 2, 3, 4, no floats
rand(0.0..5.0)
#=> one of floats 0.0 ~ 5.0
rand(1.0..5.0)
#=> one of floats 1.0 ~ 5.0