Code background grey, use special code-block for GHCi

VL1/content/VL1_lists2.tex

@@ -1,5 +1,5 @@
 Let's check on a few very common list operations:
-\begin{haskellcode}
+\begin{haskellcode*}{bgcolor=mygrey,frame=single,numbers=none,label=GHCi}
 > [1, 2] ++ [4, 5]  -- append two lists
 > head [1, 2, 3]    -- first element
 > tail [1, 2, 3]    -- everything after the head
@@ -8,12 +8,12 @@ Let's check on a few very common list operations:
 > drop 2 [1, 2, 3]  -- drop the first two elements
 > sum [1, 2, 3]
 > elem 7 [1, 2, 3]  -- is there a 7 in the list?
-\end{haskellcode}
+\end{haskellcode*}
 \pause
 A String in haskell is just a list of Chars!
-\begin{haskellcode}
+\begin{haskellcode*}{bgcolor=mygrey,frame=single,numbers=none,label=GHCi}
 > ['a', 'b', 'c']
 > 'a' : []
 > head "abc"
 > 'a' ++ 'c'
-\end{haskellcode}
+\end{haskellcode*}