Checkbox syntax

Let's suposse I have checkboxes inside a section loop so the "name" of each checkbox is: <input type="checkbox" name="{elements[$foo[ix]]}" /> I want to preserve checked boxes when processing a form in the script .. Tried something like.. <input type="checkbox" name="{elements[$foo[ix]]}" {if $smarty.request.elements[$foo[ix]]}checked="checked"{/if} /> but it doesn't work. Which is the best way to do this? Maybe I'm overlooking something more elegant.. Luis