Ruby function to return weighted boolean value

gistfile1.txt

# Given a float weight between 0 and 1, returns true that percentage of the time 
# e.g. 10.times { weighted_bool 0.3 } # should return true about 3 times 

def weighted_bool true_weight = 0.5
  raise ArgumentError.new("Weight must be a positive value less than or equal to 1.0") unless true_weight >= 0 and true_weight <= 1.0
  return rand <= true_weight
end