memoization

gistfile1.ml

let memoize f =
    let table = Hashtbl.create 10 in
    fun p -> try Hashtbl.find table p
             with Not_found ->
                 let _ = print_string "not found (memoize)\n" in
                 let v = f p in
                 let _ = Hashtbl.add table p v in
                 v

let memoize2 f =
    let table = Hashtbl.create 10 in
    fun p1 -> try Hashtbl.find table p1
              with Not_found ->
                let _ = print_string "not found (memoize2)\n" in
                let v = f p1 in
                let _ = Hashtbl.add table p1 v in
                memoize v

let memoize3 f = 
    let table = Hashtbl.create 10 in
    fun p1 -> try Hashtbl.find table p1
              with Not_found ->
                  let _ = print_string "not found (memoize3)\n" in
                  let v = f p1 in
                  let _ = Hashtbl.add table p1 v in
                  memoize2 v

(* why this doesn't work? *)
let rec memoize_gen f x =
    if x = 1
        then let table = Hashtbl.create 10 in
             fun p -> try Hashtbl.find table p
                      with Not_found ->
                          let _ = "not found\n" in
                          let v = f p in
                          let _ = Hashtbl.add table p v in
                          v
        else memoize_gen (memoize_gen f 1) (x-1)


let test =
    let fun1 = memoize_gen (fun a ->
            let _ = print_string "running the function with one param\n" in
            a) 1
    in [fun1 1; fun1 1; fun1 1]

let test2 = 
    let fun1 = memoize_gen (fun a b c ->
            let _ = print_string "running the function\n" in
            a + b + c) 3
    in [fun1 3 2 1;fun1 3 2 1; fun1 3 2 1]

let test3 =
    memoize (fun a ->
        memoize (fun b ->
            memoize (fun c -> let _ = print_string "memoized inner function\n" in
                              a + b + c)))