tut01

-- Q7
import Data.Maybe

let maxlist3 xs =
      case xs of
        [] -> Nothing;
        (x:[]) -> Just x;
        (x:ys) -> Just (max x (fromJust (maxlist3 ys)))

-- Q8
let pi = 3.14159

let multi_circle rs = case rs of {
  [] -> 0;
  (x:ys) -> pi*x^2 + multi_circle ys;
}