shuffle!

/*
 *  call-seq:
 *     array.shuffle!        -> array or nil
 *  
 *  Shuffles elements in _self_ in place.
 */


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;
}