Previous-sibling combinator

Hello.

It would be nice to have combinator to select previous sibling.

    P - UL {
        /* Styles for UL element which is
           previous sibling of P element. */
    }

The "-" combinator is functionally similar to existing "+" combinator, but selects previous-sibling element instead of next-sibling one.

So in result we would have "+" to move forward, and "-" to move backward (like element.nextSibling and element.previousSibling in DOM, respectively).

Thanks.