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

Answer 1

Let’s recap:

rand() will generate a (psuedo-)random
float between 0 and 1.

rand(int) will generate a
(psuedo-)random integer between 0 and
int.

So something like:

def range (min, max)
    rand * (max-min) + min
end

Should do nicely.

Update:

Just tested with a little unit test:

def testRange
    min = 1
    max = 100

    1_000_000.times { 
        result = range min, max
        print "ERROR" if result < min || result  > max
    }
end

Looks fine.