Simple Function to check for post type

Here is a simple usful function i use to check for a specific post type:

function is_post_type($type='post') {
 global $post_type,$typenow;

 if (isset( $_GET['post_type'] )&& $_GET['post_type'] == $type 
 || isset( $post_type ) && $post_type == $type) 
 || isset( $typenow ) && $typenow == $type) 
 return true; // return true if on a page of type $type

 return false;
}

usage:

if (is_post_type('slider')){
 // the post type is slider :)
}