lesson3.ml

(** Basic pattern matching *)

let f1 x = match x with
  | true -> 0
  | false -> 1

let f2 s = match s with
  | "aa" -> 1
  | "bb" -> 2
  | "cc" -> 3
  | _ -> 0

(* Calc, curried *)
let calc x y op = match (y, op) with
  | (_, "add") -> x + y
  | (_, "sub") -> x - y
  | (_, "mul") -> x * y
  | (0, "div") -> failwith "Division by zero."
  | (_, "div") -> x / y
  | _ -> failwith "Unknown operator."

(** Exercise : Basic pattern-matching *)

let xor a b = match (a,b) with
  | false, false -> false
  | true, true -> false
  | false, true -> true
  | true, false -> true
    
type operation = Add | Sub | Mul | Div

let calc x y op = match (y, op) with
  | (_, Add) -> x + y
  | (_, Sub) -> x - y
  | (_, Mul) -> x * y
  | (0, Div) -> failwith "Division by zero."
  | (_, Div) -> x / y

let test = calc 4 5 Mul

(** Exercise : Sequence *)

let show f v =
  Printf.printf "Function called with value %d\n%!" v ;
  f v

let pshow cv f v =
  Printf.printf "Function called with value %s\n%!" (cv v) ;
  f v

(** Exercise : Inner let *)

(* All five functions are equivalent. *)

let get_triple arg =
  match arg with
  | (a, p) ->
    begin match p with
      | (b,c) -> [ a ; b ; c ]
    end

let get_triple (a, (b, c)) = [ a ; b ; c ]


(** Exercise : Expressions *)

let fancy1 x =
  begin
    if x = 0 then
      (fun a b -> a + b )
    else
      (fun a b -> x)
  end
    (x-1) (x+1)

let fancy2 a b c =
   "Hello " ^ 

   let f =
     if a then
       match c with
       | [] -> (fun x -> string_of_int x)
       | _  -> (function 4 -> "FOUR"
                       | _ -> "NOT FOUR")
     else
       (fun _ -> "ZERO")
   in
   f b