previous_post and next_post OR previous_post_link and next_post_link?

previous_post_link() is the preferred function.

Here’s the function declaration:
function previous_post_link($format='« %link',
$link='%title',
$in_same_cat = false,
$excluded_categories = '')

So if you want to limit what gets displayed, you’ll need to first create the output yourself, then pass it as the $format or $link parameter.

i made a hack to the previous_post() and to the next_post(), maybe this is a nice feature to put in the next release version, as it is fully backwards compatible.

in template-functions-links.php replace the following two functions
function previous_post
function next_post


function previous_post($format='%', $previous='previous post: ', $title='yes', $in_same_cat='no', $limitprev=1, $excluded_categories='', $limit, $more_string) {

if ( empty($in_same_cat) || 'no' == $in_same_cat )
$in_same_cat = false;
else
$in_same_cat = true;

$post = get_previous_post($in_same_cat, $excluded_categories);

if(! $post) {
return;
}

if ((isset($limit)) && ($limit >0)) {
$s_post=substr($post->post_title,0,$limit);
if (isset($more_string)) $s_post.=$more_string;
}
else {$s_post=$post->post_title;}

$string = '<a>ID).'">'.$previous;
if ($title == 'yes') {
$string .= apply_filters('the_title', $s_post, $post);
}
$string .= '</a>';
$format = str_replace('%', $string, $format);
echo $format;
}

// Deprecated. Use next_post_link().
function next_post($format='%', $next='next post: ', $title='yes', $in_same_cat='no', $limitnext=1, $excluded_categories='', $limit, $more_string) {

if ( empty($in_same_cat) || 'no' == $in_same_cat )
$in_same_cat = false;
else
$in_same_cat = true;

$post = get_next_post($in_same_cat, $excluded_categories);

if(! $post) {
return;
}

if ((isset($limit)) && ($limit >0)) {
$s_post=substr($post->post_title,0,$limit);
if (isset($more_string)) $s_post.=$more_string;
}
else {$s_post=$post->post_title;}

$string = '<a>ID).'">'.$next;
if ($title=='yes') {
$string .= apply_filters('the_title', $s_post, $nextpost);
}
$string .= '</a>';
$format = str_replace('%', $string, $format);
echo $format;
}

the functions are called like this:

previous_post('??? %','','yes','','','',8,'(...)');
next_post(' % ???','','yes','','','',9,'(...)');

the number (7th argument) indicates the length after which the output should be cropped. (optional)
the 8th argument is the text to put after the cropping.

useful? i think so!

i posted a more modified version on https://parasew.com/hacks
the added feature is if the string is shorter than the length argument, it stays untouched.
have fun!