=begin

This is the actual C-based implementation of Array#shuffle! in ruby-1.9:

/*
 *  call-seq:
 *     array.shuffle!        -> array
 *  
 *  Shuffles elements in _self_ in place.
 */
static VALUE
rb_ary_shuffle_bang(VALUE ary)
{
    long i = RARRAY_LEN(ary);

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

# Non-destructive shuffle
def shuffle(array)
	shuffled = array.dup
	shuffle!(shuffled)
end

# Here's a basic translation of the C into Ruby
def shuffle!(array)
		
	i = array.size
		
	while i > 0 do
		random_index = rand(i)
		i -= 1
		
		temp_val = array[i]
		array[i] = array[random_index]
		array[random_index] = temp_val
	end
	
	array
end

# Let's see if it works
v = [1]
w = []
x = [1,2,3,4,5,6]
y = ["a","b","c","d"]
z = ["pretty","cool","right"]

puts "#{v} => #{shuffle(v)}"
puts "#{w} => #{shuffle(w)}"
puts "#{x} => #{shuffle(x)}"
puts "#{y} => #{shuffle(y)}"
puts "#{z} => #{shuffle(z)}"