How to best create a random float in a range between two floats

Question

I know that I can generate random floats with rand(max). I tried to generate a float in a range, this shouldn't be hard. But e.g rand(1.4512) returns 0, thus rand isn't calculating with floats. Now I tried a little trick, converting the thing to an integer and after randomizing a fitting number in my desired range, calculating it back to a float.. which is not working.

My question is how to do this in a better way. If there is no better way, why is this one not working? (Maybe it's too late for me, I should've started sleeping 2 hours ago..). The whole thing aims to be a method for calculating a "position" field for database records so users can order them manually. I've never done something like this before, maybe someone can hint me with a better solution.

Here's the code so far:

def calculate_position(@elements, index)     min = @elements[index].position      if @elements[index + 1].nil?         pos = min + 1     else         pos = min + (rand(@elements[index + 1].position * 10000000000) / 10000000000)     end      return pos end 

Thanks!

Answer 1

Pass a range of floats to rand

If you want to "create a random float in a range between two floats", just pass a range of floats to rand.

rand(11.2...76.9) 

(Tested with Ruby 2.1)

Edit

According to the documentation: https://ruby-doc.org/core-2.4.0/Random.html

There are two different ways to write the random function: inclusive and exclusive for the last value

rand(5..9)      # => one of [5, 6, 7, 8, 9] rand(5...9)     # => one of [5, 6, 7, 8] rand(5.0..9.0)  # => between 5.0 and 9.0, including 9.0 rand(5.0...9.0) # => between 5.0 and 9.0, excluding 9.0