This is probably very trival, but I need to add a class to every 4th item in a control list. For example:

<ul>
    <% control ItemList %>
        <% if nth %>
            <li class="clear-left">
        <% else %>
            <li>
        <% if_end %>
        ...
    <% end_control %>
</ul>

So for every 4th list item, what should nth be?

Is there a built in page control for this that I have missed or do I need to do something else?

Use $Pos.

$Pos will return a counter starting at 1.

How do I use $Pos in a template list control to find out it is every nth item?

So in my example, every 4th item in a list is to have a class - ie 0,4,8,12,16,20,24,28...

function Fourth()
{
return !$this->iteratorPos % 4;
}

Ok, i've gotten myself a little lost here... I've added the following

class Page_Controller extends ContentController {
...
	function IsFourthItem() {
		return !$this->iteratorPos % 4; 
	}
...
}

Is this the right place to put the function?

The following code is in the template file that generates the list...

<ul>
	<% control ItemList %> 
		<% if IsFourthItem %>
			<li class="clear-left">
		<% else %>
			<li>
		<% end_if %>
	...
	<% end_control %>
</ul>

However this does not do anything but add <li> to all list items?

Hi Hammy

Broken suggestion - This doesn't work because '%' is a reserved character I guess.

In your template file you can write:
<% control ItemList %>
<% if (($Pos % 4) == 0) %>
<li class="clear-left">
<% else %>
<li>
<% end_if %>
...
<% end_control %>

Best regards Trym

Unfortunately, when I try to use:

<% if (($Pos % 4) == 0) %> 

this is creates a "Parse error:" error when I flush the page :(

Hi Hammy

Because your code is inside at <% control ... %> element only functions in the DataObjectSet class can be used or you have to refer to $Top. The easiest way I found was to add the following function to the ViewableData.php file close to e.g. function EvenOdd().

function isForth() {
return ($this->iteratorPos + $startIndex) % 4 == 0;
}

And then in your template file write <% if isForth %>...

Best regards Trym