怎么做聪明的任务？

I tried this way,but seems not working:

{if $i == 1}
    $value = $recommend[3];
{/if}

Does smarty support assignment operation?

There is assign() method for that. Check it out here:

http://www.smarty.net/manual/en/api.assign.php

Another option besides assign() ( which is probably better from separation of code and presentation point of view) is http://www.smarty.net/manual/en/language.function.php.php

To assign variables within a template, do:

{if $i == 1}
    {assign var='value' value=$recommend[3]}
{/if}