Memoization in OCaml?

Question

It is possible to improve \"raw\" Fibonacci recursive procedure

Fib[n_] := If[n < 2, n, Fib[n - 1] + Fib[n - 2]]

with

Answer 1

You pretty much do what the mathematica version does but manually:

let rec fib = 
  let cache = Hashtbl.create 10 in
  begin fun n ->
    try Hashtbl.find cache n
    with Not_found -> begin
      if n < 2 then n
      else 
        let f = fib (n-1) + fib (n-2) in
        Hashtbl.add cache n f; f
    end
  end

Here I choose a hashtable to store already computed results instead of recomputing them. Note that you should still beware of integer overflow since we are using a normal and not a big int.