[ruby-talk:01218] Trivial FAQ bug

I wasn't sure from the intro page who is maintaining the FAQ, but I
came across a slightly subtle bug in an example:


   7.3 How can I choose 5 different numbers between 0 and 51 randomly? 

   Next method returns an array containing m randomly chosen numbers
   between 0 and n.

         def sample(n, m)
           if m.zero?
             []
           else
             s = sample(n-1, m-1)
             t = rand(n+1)
             s.concat s.include?(t) ? n : t
           end
         end

   To write it in non-recursive iterated form, 

         def sample(n, m)
           s = []
           ((n-m)...n).each do |j|
             t = rand(j+2)
             s.concat s.include?(t) ? j+1 : t
           end
           s
         end

The code fragments don't compile - concat should be '<<' or push.

Also, I think second sample also does not generate a uniform
distribution of numbers. The first time around the loop, it generates
numbers between 0 and (n-m)+2, the next time from (n-m)+3 and so on. I 
_think_ this means that the results will tend to be skewed towards the 
low side.


In general, would anyone be interested in Andy and I taking the
English FAQ and updating it? We'd be more than happy to.


Regards

Dave