Aligning the right parts in multiple \begin{cases}

Is there an intelligent way to left-align the parts right of & of the two cases environments shown below (if x >= 0, otherwise, if y < 0, otherwise). I wonder if there is a better way than using manual spaces:

\begin{align*}
u(x) &=
\begin{cases}
0        & \text{if } x \geq 0 \\
1        & \text{otherwise}
\end{cases}
\\
\tau &=
\begin{cases}
a+b+c+d  & \text{if } y < 0 \\
1        & \text{otherwise}
\end{cases}
\end{align*}


-
The easiest solution I can come up with is to use the mathtools package and use something like \mathrlap0\hphantom{a+b+c+d} in place of your 0. But that's playing with manual spacing, I suppose. –  TH. Sep 21 '10 at 2:04
You can use the solutions to an earlier question, just exchanging the order of the statements. –  Caramdir Sep 21 '10 at 2:09
Both great. Thanks. Much better than fiddling with manual \quad-s etc. –  Frank Seifert Sep 21 '10 at 2:16
@TH, @Caramdir: Why not post actual answers? –  SamB Sep 27 '10 at 21:14
@TH, @Caramdir: If you can put up an answer or two, as @SamB suggests, then we can shift this qn off the "Unanswered" list. –  Charles Stewart Oct 5 '10 at 7:54

1 Answer

You can use the solutions to an earlier question, just exchanging the order of the statements.

Another solution is to use the mathtools package and use something like \mathrlap0\hphantom{a+b+c+d} in place of your 0.

-