static VALUE
enum_partition(VALUE obj)
{
    VALUE ary[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    ary[0] = rb_ary_new();
    ary[1] = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, partition_i, (VALUE)ary);

    return rb_assoc_new(ary[0], ary[1]);
}