shuffling arrays for 1.8.6

ruby_shuffle.c

static VALUE
rb_ary_shuffle_bang(ary)
    VALUE ary;
{
    long i = RARRAY(ary)->len;

    rb_ary_modify(ary);
    while (i) {
        long j = rb_genrand_real()*i;
        VALUE tmp = RARRAY(ary)->ptr[--i];
        RARRAY(ary)->ptr[i] = RARRAY(ary)->ptr[j];
        RARRAY(ary)->ptr[j] = tmp;
    }
    return ary;
}

ruby_shuffle.rb

class Array
  def shuffle!
    i = size
    while(i>0)
      j = rand() * i
      tmp = self[(i-=1)]
      self[i] = self[j]
      self[j] = tmp
    end
    self
  end
end

# I think I like this one the best:
class Array
  def shuffle!
    size.times do |i|
      j = i + rand(size - i)
      self[i], self[j] = self[j], self[i]
    end
    self
  end
end

ruby_shuffle_parallel_assignment.rb

# It works, and it's harder to read to boot - @jaknowlden
class Array
  def shuffle!
    i = size
    while(i>0)
      j,i = rand() * i, (i-1)
      self[i], self[j] = self[j], self[i]
    end
    self
  end
end

ruby_shuffle_rubinius.rb

#this takes advantage of rubinius' Tuple class. Left here as an example.
  # Shuffles elements in self in place.
  def shuffle!
    size.times do |i|
      r = i + Kernel.rand(size - i)
      @tuple.swap(i,r)
    end
    self
  end