answers.ml

Download file: answers.ml
(*** Keep these lines. ***)
let qfile = "qqs.ml" ;;
let formatter = Format.(make_formatter (fun _ _ _ -> ()) (fun () -> ())) ;;
Topdirs.dir_use formatter (if Sys.file_exists qfile then qfile else Sys.getenv "HOME" ^ "/Exam-OCaml/" ^ qfile) ;;

(************************************)


(*****  QUESTION 1  *****)

let f1 g l = List.fold_left (fun acu x -> acu + g x) 0 l

let () = q1 { ff = f1 }


(*****  QUESTION 2  *****)

let f2 g x = ( g x (fun f y -> f y x) ) 

let () = q2 { ff = f2 }


(*****  QUESTION 3  *****)

let f3 g y = function
  | None -> y
  | Some z -> g z

let () = q3 { ff = f3 }


(*****  QUESTION 4  *****)

let rec f4 g = function
  | [] -> []
  | A x :: rest -> let tail = f4 g rest in (try g x :: tail with _ -> tail)
  | B x :: rest -> g x :: f4 g rest

let () = q4 { ff = f4 }


(*****  QUESTION 5  *****)

let f5 f l = List.for_all (function A _ -> true | B y -> f y) l

let () = q5 { ff = f5 }


(*****  QUESTION 6  *****)

let f6 l =
  let alla = List.filter_map (function A x -> Some x | _ -> None) l in

  let rec loop alla l =
    match (alla, l) with
      | [], [] -> []
      | xa :: xrest, A y :: rest -> A xa :: loop xrest rest
      | _, B y :: rest -> B y :: loop alla rest
      | [], A _ :: _ -> assert false
      | _ :: _, [] -> assert false
  in

    loop (List.rev alla) l

let () = q6 { ff = f6 }


(*****  QUESTION 7  *****)

let rec f7 f = function
  | Aleaf x -> Aleaf x
  | Bleaf y -> if f y then Aleaf y else Bleaf y
  | Node (left, right) -> Node (f7 f left, f7 f right)

let () = q7 { ff = f7 }


(*****  QUESTION 8  *****)

let rec f8 t1 t2 =

  match t1, t2 with
    | Aleaf x, Aleaf y -> if x <> y then Some (t1, t2) else None
    | Bleaf x, Bleaf y -> if x <> y then Some (t1, t2) else None

    | Aleaf _, _
    | Bleaf _, _
    | _, Aleaf _
    | _, Bleaf _ -> Some (t1, t2)

    | Node (l1, r1), Node (l2, r2) ->
        begin match f8 l1 l2 with
          | None -> f8 r1 r2
          | Some z -> Some z
        end

let () = q8 { ff = f8 }