query only parents, without child pages

My purpose is to select pages to use them in the loop, can you do that with the function you linked me ?

I solved my problem. I simply used a condition :

<?php
query_posts( 'post_type=page' ); // select all the pages
if (have_posts() ) :
while (have_posts() ) : the_post();
if ( ! $post->post_parent ) : // filter the pages without parent
?>

<!-- THE LOOP -->